Issued  Juru£l4,  ,1911. 


U.  S.  DEPARTMENT  OF  j\GRICULTURg, 

BUREAU  OF  ANIMAL  INDUSTRY.— BULLETIN  130.          & 

=-  <4 


A.  D.  MELVIN,  CHIEF  OF  BUREAU. 


JDIES  ON  THE  BIOLOGY  OF 
THE  TEXAS-FEVER  TICK. 


BY 


H.  W.  GRAYBILL, 

Assistant  Zoologist,  Zoological  Division, 
Bureau  of  Animal  Industry. 


UNIVERSITY  OF  CALIFORNIA* 
LOS  ANGELES 

SEP  23  1952 


LIBRARY 
GOYT.  PUBS.  ROOM 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 
1911. 


Ksm-il  June  14,  1911. 

U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY.— BULLETIN  130. 

A.  D.  MELVIN,  CHIEF  OF  BUREAU. 


STUDIES  ON  THE  BIOLOGY  OF 
THE  TEXAS-FEVER  TICK. 


BY 


H.  W.  GRAYBILL, 

Assistant  Zoologist,  Zoological  Division, 
Bureau  of  Animal  Industry. 


WASHINGTON: 
GOVERNMENT  PRINTING  OFFICE. 

1911. 


THE    BUREAU    OF   ANIMAL    INDUSTRY. 


Chief:  A.  D.  MELVIN. 
Assistant  Chief:  A.  M.  FARRINGTON. 
Chief  Clerk:  CHARLES  C.  CARROLL. 

Animal  Husbandry  Division:  GEORGE  M.  ROMMEL,  chief. 
Biochemic  Division:  M.  DORSET,  chief. 
Dairy  Division:  B.  H.  RAWL,  chief. 

Inspection  Division:  RICE  P.  STEDDOM,  chief;  MORRIS  WOODEN,  R.  A.  RAMSAY, 
and  ALBERT  E.  BEHNKE,  associate  chiefs. 

Pathological  Division:  JOHN  R.  MOHLER,  chief. 
Quarantine  Division:  RICHARD  W.  HICKMAN,  chief. 
Zoological  Division:  B.  H.  RANSOM,  chief. 
Experiment  Station:  E.  C.  SCHROEDER,  superintendent. 
Editor:  JAMES  M.  PICKENS. 

ZOOLOGICAL    DIVISION. 

Chief:  B.  H.  RANSOM. 

Assistant  Zoologists:  ALBERT  HASSALL,  HARRY  W.  GRAYBILL,  and  MAURICE  C.  HALL. 

Junior  Zoologists:  HOWARD  CRAWLEY  and  WINTHROP  D.  FOSTER. 


LETTER  OF  TRANSMITTAL. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY, 

Washington,  D.  C.,  September  28,  1910. 

SIR:  I  have  the  honor  to  transmit  for  publication  the  accompanying 
manuscript  entitled  "Studies  on  the  Biology  of  the  Texas-fever 
Tick,"  by  H.  W.  Graybill,  assistant  zoologist  in  the  Zoological  Divi- 
sion of  this  bureau. 

A  large  number  of  publications  have  been  issued  from  time  to  time 
regarding  the  investigations  of  this  bureau  concerning  the  Texas- 
fever  tick  and  its  disastrous  effect  upon  the  cattle  industry  of  the 
South,  and  the  extermination  of  the  parasite  has  in  recent  years 
been  vigorously  pushed  both  by  the  Federal  Government  and  the 
several  States  involved.  In  order  that  this  work  of  extermination 
may  be  the  more  intelligently  and  successfully  carried  out  it  is 
necessary  that  it  should  be  based  upon  the  most  accurate  knowledge 
possible  of  the  life  history,  habits,  etc.,  of  the  tick.  Accordingly 
the  experiments  herein  described  were  projected  in  order  to  add 
further  information  relative  to  certain  biological  features  of  the  tick 
which  may  have  a  bearing  upon  the  eradication  work.  The  experi- 
ments were  carried  out  in  cooperation  with  the  veterinary  depart- 
ment of  the  Alabama  Polytechnic  Institute,  at  Auburn,  Ala. 

I  recommend  that  the  paper  be  published  in  the  bulletin  series  of 
this  bureau. 

Respectfully,  A.  D.  MELVIN, 

Chief  of  Bureau. 

Hon.  JAMES  WILSON, 

Secretary  of  Agriculture. 


CONTENTS. 


Page. 

Introduction 7 

Historical 7 

Methods  of  study 9 

Periods  of  the  nonparasitic  portion  of  development 12 

The  preoviposition  period 12 

The  oviposition  period 13 

Incubation  period 14 

Hatching  period 15 

Longevity  period 16 

Total  time  of  nonparasitic  development 17 

Number  of  eggs  laid  and  percentage  hatched 18 

Experiments  with  horizontal  tubes 19 

Records  obtained  from  the  field  plots 20 

Per  cent  of  females  ovipositing 22 

Effect  of  immersion  in  water  on  engorged  females 23 

The  influence  of  moisture  on  the  incubation  period 23 

Periods  in  the  parasitic  portion  of  development 24 

Observations  on  the  movement  of  ticks  after  the  first  and  second  molt 26 

.  Change  of  location  after  first  molt 26 

Change  of  location  after  second  molt 27 

Early  distinguishing  of  female  nymphs  by  males 27 

Experiments  in  transferring  ticks  on  cattle 27 

Experiments  in  rearing  unfertilized  females 29 

The  occurrence  of  dead  ticks  on  cattle 31 

Host  relations  of  the  cattle  tick 31 

Infestation  experiments  on  rabbits 32 

Infestation  experiments  on  a  cat 33 

Infestation  experiment  on  a  dog 33 

Infestation  experiments  on  sheep 33 

The  natural  occurrence  of  the  cattle  tick  on  sheep 34 

The  progeny  of  females  matured  on  sheep  noninfectious 36 

Man  as  a  host  of  the  tick 37 

Bibliography 3S 

Appendix: 

TABLE  1 .  Individual  records  of  ticks  used  in  experiments 40 

TABLE  2.  Data  on  parasitic  development  of  ticks  on  animals 42 

5 


ILLUSTRATIONS. 


Page. 
FIG  .  1 .  Vertical  tube  used  for  incubating  eggs  of  tick 3 9 

2.  Horizontal  tube  used  for  incubating  eggs  of  ticks 10 

3.  Arrangement  of  field  plot  for  incubating  tick  eggs  under  outdoor  con- 

ditions          12 

6 


STUDIES  ON  THE  BIOLOGY  OF  THE  TEXAS-FEVER  TICK. 


INTRODUCTION. 

The  eradication  of  the  cattle  tick  ( Margaropus  annulatus)  from  the 
States  below  the  quarantine  line  has  been  shown  to  be  entirely  feasible 
as  a  result  of  the  work  carried  on  during  the  past  five  years  by  the 
Bureau  of  Animal  Industry  in  cooperation  with  the  State  authorities. 
The  work  of  extermination  must,  obviously,  be  preceded  by  and  based 
upon  a  knowledge  of  the  life  history  of  the  tick,  its  habits,  and  the 
manner  in  which  it  is  affected  by  climatic  and  other  environmental 
conditions. 

In  order  to  supply  possibly  useful  data  relative  to  the  biology  of 
the  tick,  additional  to  that  already  collected  by  different  observers, 
a  series  of  investigations  was  arranged  for  and  carried  out  under 
cooperation  between  the  Zoological  Division  of  this  bureau  and  the 
veterinary  departhient  of  the  Alabama  Polytechnic  Institute  at 
Auburn,  Ala.  In  the  observational  part  of  these  investigations,  the 
results  of  which  are  recorded  in  the  present  paper,  the  writer  was 
assisted  by  Mr.  W.  M.  Lewallen.  Some  of  the  results  of  the  work  at 
Auburn  have  been  briefly  mentioned  in  an  earlier  paper  (Graybill, 
1909)10.a 

HISTORICAL. 

Up  to  the  time  that  Dr.  Cooper  Curtice2  (1891)  of  this  bureau 
established  the  fundamental  facts  in  the  life  history  of  the  cattle  tick 
it  was  commonly  assumed  that  the  life  history  of  this  species  corre- 
sponded to  that  of  certain  other  ticks,  which  fall  from  their  host 
before  shedding  their  skins  in  transforming  from  one  stage  to  another. 
Curtice,  however,  showed  that  the  cattle  tick  remains  on  the  host 
from  the  time  it  attaches  as  a  larva  until  it  falls  as  an  engorged 
female  to  deposit  its  eggs,  and  established  other  facts  relative  to  the 
duration  of  some  of  the  periods  in  the  life  cycle  and  the  changes  in 
structure  occurring  at  the  time  of  the  first  and  second  molts,  which 
were  supplemented  in  a  second  paper3  (1892)  by  further  data  concern- 
ing the  life  history,  habits,  and  structure  of  the  tick.  Smith  and 
Kilborne22  (1893),  who  were  the  first  to  demonstrate  and  prove  the 
connection  between  the  tick  and  Texas  fever,  published  a  number 

a  Citations  to  literature  are  given  In  bibliography  on  page  3S. 
89053°— Hull.  130—11 2 


8  BIOL.OGY    OF    THE    TEXAS-FEVER   TICK. 

of  important  facts  on  the  biology  of  this  parasite,  and  Schroeder  18> 19 
(1900  and  1907)  and  Schroeder  and  Cotton20-  21  (1900  and  1907)  in 
several  articles  issued  by  this  bureau  have  presented  considerable 
data  bearing  on  the  life  history  of  the  tick  and  its  relationship  to  the 
disease  which  it  transmits.  Curtice5  (1896)  was  among  the  first  to 
urge  the  undertaking  of  eradication  measures,  and  (1897)6  was  the 
first  to  show  how  cattle  could  be  freed  from,  ticks  by  rotation  methods. 
Doctor  Curtice's  work  in  North  Carolina,  continued  by  Dr.  Tait 
Butler,  clearly  demonstrated  at  an  early  date  the  feasibility  of  tick 
eradication,  which  has  been  fully  confirmed  by  the  experience  of  the 
more  extensive  campaign  now  under  way  in  various  parts  of  the 
tick-infested  area. 

Several  investigators  connected  with  State  experiment  stations  have 
studied  the  tick  with  reference  to  its  life  history.  Dinwiddie  8  (1892), 
of  the  Arkansas  Experiment  Station,  was  an  early  investigator,  who 
more  recently  (1908) 9  has  published  further  observations.  Morgan 
(in  Dalrymple,  Morgan,  and  Dodson,7  1898)  reported  investigations 
conducted  in  Louisiana  having  to  do  with  various  stages  of  the 
tick,  especially  with  regard  to  the  influence  of  heat,  cold,  and  light 
and  the  effects  of  water  upon  the  tick  and  its  eggs.  Later  the  same 
author14'15  (1903,  1905)  discussed  and  emphasized  the  practicability 
of  freeing  cattle  and  pastures  of  ticks  by  following  pasture-rotation 
methods  based  upon  known  facts  in  the  life  history. 

Newell  and  Dougherty16  (1906),  of  the  State  Crop  Pest  Commission 
of  Louisiana,  made  a  comprehensive  study  of  various  periods  in  the  life 
cycle,  obtaining  valuable  data  on  the  duration  of  the  incubation  period 
and  the  vitality  of  the  larvas,  at  different  times  of  the  year.  Their 
work  was  conducted  at  Baton  Rouge,  La.,  and  they  formulated  a 
pasture-rotation  method  for  ridding  cattle  and  farms  of  ticks,  adapted 
to  conditions  prevailing  in  Louisiana.  Cotton1  (1908),  of  the  Ten- 
nessee Experiment  Station,  has  published  life-history  notes  based  on 
investigations  conducted  at  Knoxville,  Tenn.,  and  has  suggested  a 
number  of  rotation  methods  for  tick  eradication. 

Recently  the  Bureau  of  Entomology  of  this  department  has  under- 
taken life-history  studies  of  the  tick  and  has  issued  Bulletin  72,  by 
Hunter  and  Hooker12  (1907),  in  which  are  incorporated  the  results  of 
comprehensive  investigations  conducted  by  these  authors  at  Dallas, 
Tex.  The  results  obtained  by  these  investigators  are  confirmatory  of 
the  earlier  work  of  the  Bureau  of  Animal  Industry  and  other  observers, 
and  in  addition  have  largely  increased  our  knowledge  of  the  biology 
of  the  tick,  supplying  data  concerning  all  stages  of  development, 
time  required  for  the  completion  of  these  stages  at  different  seasons 
of  the  year,  and  the  influence  of  variations  in  environment,  together 
with  suggestions  for  the  practical  application  of  the  information  given. 


THE    EGG    INCUBATION    TUBES. 


METHODS    OF    STUDY. 

The  plan  pursued  in  determining  the  incubation  period  of  dggs  and 
the  longevity  of  seed  ticks  in  the  investigations  at  Auburn  was  essen- 
tially that  followed  by  Newell  and  Dougherty1"  :100G).  A  number 
of  engorged  females  were  collected  at  the  beginning  of  each  month. 
After  oviposition  began  the  eggs  laid  by  each  tick  were  removed  at 
the  end  of  every  24  hours.  After  they  were  counted  each  lot  was 
placed  in  an  incubation  tube  marked  with  the  date  when  removed 
and  a  number  indicating  the  tick  which  deposited  them.  Careful 
observations  were  made  on  the  tubes  and  a  record  was  kept  of  the 
time  when  the  eggs  in  each  tube  began  to  hatch  and  when  the 
hatching  was  completed,  also  when  the  larva1 
began  to  die  and  when  all  of  them  were  dead. 

At  the  outset  of  the  work  the  incubation  tubes 
used  were  test  tubes  of  the  type  employed  in 
bacteriological  work.  These  were  filled  half  full 
of  moist  sand.  A  cardboard  disk  cut  so  as  to 
fit  the  tube  was  pressed  down  on  the  sand.  On 
top  of  this  was  placed  a  small  cube  of  cork,  and 
on  the  latter  was  placed  another  disk  similar  to 
the  first.  The  eggs  were  placed  on  the  upper 
disk.  It  was  found  necessary  to  use  these  disks 
in  order  to  prevent  the  eggs  and  seed  ticks  from 
becoming  mixed  with  the  sand,  which  would  have 
rendered  observation  very  difficult  and  also 
would  have  made  the  counting  of  the  unhatched 
eggs  and  dead  seed  ticks,  for  the  purpose  of  deter- 
mining the  percentage  of  eggs  hatching,  an  almost 
impossible  task.  Furthermore,  if  only  one  disk 
is  used  the  development  of  the  eggs  is  frequently 
endangered  by  the  growth  of  mold.  When  the 
two  are  used,  separated  in  the  manner  indi- 
cated, mold  frequently  grows  on  the  lower  one, 
but  does  not  often  attack  the  upper  one  in 
such  a  manner  as  to  endanger  the  eggs. 

These  tubes,  however,  were  not  found  entirely 
satisfactory  on  account  of  the  fact  that  there 

was  no  practicable  way  of  adding  more  water  to  the  sand  and  thus 
keeping  the  tube  supplied  with  moisture.  To  obviate  this  defect  a 
new  tube  was  devised  which  was  found  very  satisfactory  in  most  re- 
spects (see  fig.  1).  It  is  so  constructed  that  it  is  possible  to  add 
water  to  the  sand  at  any  time.  The  new  tubes  are  made  of  glass 
cylinders  11.5  cm.  long  and  about  20  mm.  in  outside  diameter. 
One  end  of  the  cylinder  is  closed  by  a  cork,  pierced  in  the  middle  by  a 


FIG.  ].— Vertical  tul>e  u 
for  incubating  ejrtrs 
ticks. 


10  BIOLOGY    OF    THE    TEXAS-FEVER   TICK. 

hole  about  5  mm.  in  diameter.  Into  this  opening  is  fitted  one 
arm  of  a  piece  of  glass  tubing  bent  in  the  form  of  a  hook.  This 
arm  should  be  long  enough  to  pass  through  the  cork  and  the 
bend  should  be  just  so  broad  that  the  long  arm  runs  up  close  to  the 
outside  of  the  glass  cylinder.  The  long  arm  should  reach  to  about 
the  middle  of  the  tube.  Water  is  added  through  this  portion  of  the 
tubing.  The  cardboard  disks  are  arranged  in  the  same  manner  as 
in  the  test  tubes  previously  described,  the  only  modification  necessary 
being  to  pierce  the  disks  with  a  needle  in  order  to  permit  the  escape 
of  air  from  below  upward  when  water  is  added.  In  case  the  short 
arm  of  the  tubing  becomes  clogged  with  sand  the  tubing  is  easily 
removed  and  flushed  out  with  water.  The  incubation  tubes  were 
closed  on  top  by  means  of  muslin  held  in  place  by  rubber  bands. 
Cheese  cloth  is  not  satisfactory  for  this  purpose,  being  so  loosely  woven 
that  the  larvse  escape  through  the  openings. 

During  the  course  of  the  work  a  much  simpler  method  than  the 
above  for  obtaining  records  on  the  nonparasitic  stages  of  the  tick 


FIG.  2.— Horizontal  tube  for  incubating  eggs  of  ticks. 

was  devised.  In  this  method  a  horizontal  tube  is  used  (see  fig.  2). 
This  is  made  of  a  glass  cylinder  like  that  described  above.  A  cork  is 
inserted  in  one  end.  On  the  bottom  of  the  cork  a  rectangular  piece 
of  cardboard  is  fastened  so  that  one  of  its  Jong  sides  projects  a  little 
beyond  the  edge  of  the  cork  and  serves  as  a  support  for  the  tube, 
preventing  it  rolling  from  side  to  side.  The  tube  contains  a  tray 
constructed  as  follows:  A  rectangular  piece  of  rather  thick  paper, 
with  a  width  equal  to  one-half  the  inside  circumference  of  the  tube 
and  a  length  equal  to  the  internal  length  of  the  tube,  is  provided 
for  the  bottom  and. sides.  The  ends  are  made  of  thin  disks  of  cork 
having  a  diameter  a  little  less  than  the  internal  diameter  of  the  tube. 
The  rectangular  piece  of  paper  is  rolled  into  a  half  cylinder  and  the 
cork  ends  are  pinned  or  glued  into  position,  each  tilting  a  little 
toward  the  other.  One  of  the  disks  is  placed  some  little  distance  from 
the  end  of  the  tray,  a  fingerhold  being  thus  afforded  for  withdrawing 
it  from  the  tube.  The  end  of  the  tube  is  covered  with  a  piece  of 
muslin. 


METHODS    OF   STUDY.  11 

This  particular  form  of  horizontal  tube  was  kept  when  in  use 
beneath  a  bell  jar  supplied  with  moisture.  Another  variety  with 
sand  in  the  end  next  the  cork  and  fitted  with  a  piece  of  glass  tubing 
for  the  addition  of  wrater,  as  in  the  vertical  incubation  tubes,  was  also 
used.  These  latter  tubes  furnished  conditions  practically  identical 
with  those  in  the  vertical  tubes.  Various  modifications  of  these 
horizontal  tubes  were  used,  some  being  made  of  ordinary  test  tubes, 
but  they  are  hardly  of  sufficient  importance  to  be  described  here. 

The  method  of  using  the  horizontal  tube  is  as  follows:  An  en- 
gorged female  is  placed  in  the  tray,  which  is  put  in  the  tube.  The 
tilted  ends  prevent  the  tick  from  crawling  up.  After  oviposition 
begins  the  tick  moves  slowly  backward,  leaving  a  long  mass  of  eggs 
in  front  of  it.  When  oviposition  is  nearly  completed  the  female  is 
removed  from  the  eggs  to  the  opposite  end  of  the  tray,  so  as  to  facili- 
tate observation  of  the  remainder  of  the  process.  The  newly  laid 
eggs  are  removed  from  her  each  day  and  placed  at  the  end  of  the  egg 
mass  until  oviposition  is  completed.  The  hatching  proceeds  along 
the  mass  of  eggs  until  the  last  hatch,  unless,  as  sometimes  happens, 
there  is  a  displacement  of  the  eggs.  The  dates  when  the  female  was 
collected,  when  oviposition  began  and  ended,  when  hatching  began 
and  was  completed,  and  when  the  first  and  the  last  larvae  died  are 
recorded.  This  method  requires  such  a  small  amount  of  time  daily 
in  attending  to  the  tubes  that  a  very  large  number  of  ticks  can  be 
kept  under  observation  at  one  time  and  under  various  conditions. 

For  the  purpose  of  checking  the  results  obtained  in  the  tubes 
indoors,  experiments  were  conducted  outside  in  sunny  and  shady 
places  presenting  ordinary  pasture  conditions.  In  these  experiments 
small  plots  in  a  pasture  were  used  (fig.  3).  Each  plot  consisted  of 
an  area  2  feet  square  inclosed  by  boards  3  inches  wide  set  edgewise. 
In  the  center  of  the  plot  an  ordinary  cigar  box  with  the  lid  and  bottom 
removed  was  sunk  halfway  into  the  turf.  This  was  done  so  -as  to 
confine  the  female  ticks  and  thus  facilitate  observation  on  them. 
The  box  was  provided  with  a  cover  made  of  screen  wire,  which,  during 
the  progress  of  the  experiment  was  covered  over  with  dead  leaves 
or  other  litter.  The  plots  were  protected  from  surface  drainage  by 
properly  arranged  ditches.  Each  was  surrounded  by  a  fence  of  wire 
netting  to  keep  out  animals.  There  were  two  series  of  these  plots, 
one  in  a  place  shaded  by  trees  for  a  part  of  the  day  and  the  other  in 
an  unshaded  place. 

The  indoor  experiments  were  conducted  in  an  unheated  room  with 
the  windows  open  at  all  times  as  high  as  was  practicable.  The  tem- 
perature and  humidity  were  thus  made  to  correspond  very  closely 
to  outdoor  conditions. 

The  experiments  in  the  plots  were  run  parallel  with  the  indoor 
experiments  Usually  two  plots  were  started  at  the  beginning  of 


12  BIOLOGY    OF   THE   TEXAS-FEVER   TICK. 

each  month.  Ordinarily  10  engorged  ticks  were  confined  in  the 
box  described  above  and  observations  were  continued  on  each  plot 
until  it  became  free  of  seed  ticks. 

PERIODS  OF  THE  NONPARASITIC  PORTION  OF  DEVELOPMENT. 

The  various  periods  in  the  nonparasitic  portion  of  the  development 
of  the  tick  which  will  receive  consideration  in  the  following  pages  are, 
the  preoviposition  period,  the  oviposition  period,  the  incubation 
period,  the  hatching  period,  and  the  longevity  of  the  larvae;  also  the 


FIG.  3.— Arrangement  of  field  plot  for  Incubating  tick  eggs  under  outdoor  conditions. 

entire  period  from  the  time  the  female  drops  until  all  the  larvae  are 
dead.  Unless  otherwise  specified  the  records  given  hereafter  refer 
to  the  experiments  in  the  vertical  tubes. 

THE    PREOVIPOSITION    PERIOD. 

This  period,  so  named  by  Hunter  and  Hooker12  (1907,  p.  14), 
extends  from  the  time  the  female  tick  drops  until  she  begins  to 
oviposit.  Its  duration  was  found  to  vary  greatly  for  the  different 
months  of  the  year,  depending  largely  on  the  temperature.  The 
average  length  of  the  period,  as  shown  in  the  following  tables,  ranged 
from  3  to  49.3  days.  The  maximum  period  observed  was  98  days 
and  the  minimum  1  day.  The  latter  is  not  included  in  the  tables, 


THE   OVIPOSTTION    PERIOD. 


13 


as  it  was  observed  outside  the  course  of  the  regular  experiments.  It 
occurred  in  the  case  of  a  moderate-sized  tick  collected  April  29,  190X, 
which  had  been  placed  in  a  flask  along  with  some  others. 

During  the  preoviposition  period  the  ticks  under  observation  were 
kept  either  in  petri  dishes,  the  bottoms  of  which  were  lined  with 
paper,  in  pasteboard  boxes,  or  in  horizontal  tubes.  The  results 
obtained  relative  to  the  preoviposition  period,  arranged  according  to 
the  months  during  which  the  ticks  were  collected,  are  given  in  the 
following  tables: 

Preoviposition  period — Range  and  average  length  of  periods. 
VERTICAL-TUBE  EXPERIMENTS. 


Date  ticks  were 
collected. 

Number 
of  ticks. 

Range  of 
periods. 

A  verage 
of  periods. 

Date  ticks  were 
collected. 

Number 
of  ticks. 

Range  of 
periods. 

Average 
of  periods. 

1907. 
June  1  

7 

Days. 
tj  to   9 

Days. 
1 

1908. 
Jan.  1  29  and  30... 

Days. 
34  to  1)3 

Day*. 
41.2 

July  1  

7 

3  to    4 

3.9 

Feb.  3,  4,  27,  and  28. 

8  to  30 

22.2 

\ug.  1  and  31  

14 

2  to    4 

3.1 

Mar.  20  and  29.    ... 

9 

4  to    8 

5.2 

Oct  1 

7 

4  to    ti 

4  3 

Apr.  29    

14 

4  to    7 

5  9 

Nov.  1  and  30. 
Dec.  29         

11 
3 

7  to  9S 
39  to  03 

30.5 
49.3 

HORIZONTAL-TUBE  EXPERIMENTS. 


1907. 
Aug  31 

4 

3 

3 

1908. 
Feb.  3,  24,27,and28. 

, 

10  to  33 

18.3 

Oct  1              

4 

4 

Mar.  1,  3,  23,  and  25. 

7 

5  to  11 

7 

Nov.  1  and  26  

5 

9  to  33 

18.2 

Apr.  29  and  30. 

10 

5  to   8 

6.5 

Dec  25 

2 

27  to  33 

30 

May  1     

0 

5  to   9 

C.I 

In  both  tables  it  is  seen  that  the  highest  average  is  for  the  mont  h 
of  December  and  the  lowest  for  the  month  of  August. 

THE    OVIPOSITIOX    PERIOD. 

The  duration  of  this  period  depends  on  the  temperature,  and  to  a 
less  degree  on  a  number  of  other  things,  such  as  state  of  engorgement, 
number  of  eggs  laid,  etc.  The  ticks  used  were  always  good  specimens, 
as  near  complete  engorgement  as  it  was  practicable  to  obtain.  The 
average  oviposition  period  for  different  months  of  the  year,  as  shown 
in  the  following  table,  ranged  from  8.3  days  for  June,  1907,  to  127.5 
days  for  November  of  the  same  year.  The  maximum  period  noted  was 
152  days  and  the  minimum  3  days,  observed  in  the  case  of  ticks 
which  began  ovipositing  in  November  and  June,  respectively. 


14  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 

Oviposition  period — Range  and  average  length  of  periods. 
VERTICAL-TUBE  EXPERIMENTS. 


Month  oviposition 
began. 

Number 
of  ticks. 

Range  of 
periods. 

Average 
of  periods. 

Month  oviposition 
began. 

Number 
of  ticks. 

Range  of 
periods. 

Average 
of  periods. 

1907. 
June  

Days. 
3  to   14 

Days. 
8  3 

1908. 
January 

2 

Days. 
54  to  87 

Days. 
70  5 

July 

4  to    20 

12  9 

3 

37  to  63 

46  7 

August       

12  to   19 

15.6 

March 

14 

17  to  43 

30  2 

September  

14  to    19 

16.5 

April       

7 

14  to  35 

24  9 

October 

21  to    37 

32  9 

Mav 

14 

19  to  27 

22  8 

November  

78  to  151 

98.4 

HORIZONTAL-TUBE  EXPERIMENTS. 


1907. 
September 

(j 

9  to    21 

15 

1908. 
January 

4 

73  to  91 

79 

October      .... 

4 

22  to    37 

29.7 

March       

16 

26  to  49 

34.6 

November 

4 

83  to  152 

127.5 

April 

1 

24 

24 

Mav           

16 

15  to  24 

20.8 

INCUBATION    PERIOD. 

The  duration  of  this  period  depends  principally  on  the  temperature. 
It  was  found  to  range  from  19  days  in  the  summer  to  180  days  begin- 
ning in  the  fall.  Low  temperatures  not  only  retard  but  even  may 
arrest  temporarily  or  permanently  the  development  of  the  eggs. 
Moisture,  although  necessary  to  development,  has  but  a  small  influ- 
ence, if  any,  on  the  rate  at  which  this  takes  place. 

The  conditions  essential  to  the  development  and  eventual  hatch- 
ing of  eggs  are  a  proper  supply  of  moisture  and  a  favorable  tempera- 
ture. All  that  is  required  in  the  way  of  moisture  is  a  sufficient 
atmospheric  humidity  to  prevent  eggs  losing  moisture  by  evaporation. 
With  regard  to  temperature  it  may  be  said  that  the  maximum,  mini- 
mum, and  optimum  temperatures  for  development  of  the  eggs  have 
not  been  determined.  Hunter  and  Hooker12  (1907)  have  assumed 
43°  F.  as  the  minimum,  but  this  has  not  yet  been  verified  by  experi- 
ment. Eggs  are  frequently  killed  by  the  low  temperatures  occurring 
during  the  winter  months,  although  those  that  have  been  incubated 
for  a  time  are  less  susceptible  to  the  ill  effects  of  cold  than  those  newly 
laid. 

As  has  been  previously  stated,  the  eggs  were  removed  from  each 
female  tick  at  the  end  of  every  24  hours  and  placed  in  vertical  tubes. 
A  record  was  kept  of  the  date  each  lot  was  laid,  the  date  the  eggs 
began  to  hatch,  and  the  date  they  completed  hatching.  The  latter 
date  is,  however,  only  approximately  correct,  since  it  is  not  possible 
to  determine  accurately  when  all  the  eggs  of  a  lot  have  hatched,  on 
account  of  the  fact  that  some  eggs  having  all  the  marks  of  viability 
frequently  fail  to  hatch.  By  using  the  three  dates  just  mentioned, 
two  incubation  periods  were  determined  for  each  lot  of  eggs,  which 


THE   HATCHING   PERIOD. 


15 


are  referred  to  here  as  the  maximum  and  minimum.  The  range  of 
the  incubation  periods  of  the  eggs  laid  by  each  tick  is  given  in  Table  1 
of  the  Appendix.  The  range  of  the  minimum  incubation  periods  and 
the  averages  for  each  month,  from  June,  1907,  to  May,  1908,  are  given 
in  the  following  table: 

Incubation  period — Range  and  average  length  of  minimum  incubation  periods. 


Month  eggs 
deposited. 

Number 
of  lots. 

Range  of 
periods. 

Average 
of  periods. 

Month  eggs 
deposited. 

Number 
oflots. 

Range  of 
periods. 

Average 
of  periods. 

1907. 
June          

60 

Days. 
22  to   27 

Days. 
24.5 

1908. 
February  

1 

Days. 
80 

Days. 

80 

July       

82 

19  to   24 

20.5 

March  

270 

46  to  63 

52.7 

August 

90 

19  to   24 

21.2 

April  

197 

36  to  53 

43.6 

September 

81 

28  to    64 

35.9 

May  

279 

23  to  34 

26.3 

October           

145 

165  to  180 

173.1 

November  

31 

148  to  170 

155.5 

December  

7 

117  to  139 

128.  6 

From  the  above  table  it  is  seen  the  averages  increase  from  July  to 
October,  1907,  and  decrease  from  November,  1907,  to  May,  1908.  The 
average  for  June,  1907,  being  higher  than  for  July,  which  marks  the 
beginning  of  the  increase,  indicates  that  the  average  for  the  latter 
month  is  the  lowest  that  would  have  been  obtained  had  the  experi- 
ments covered  the  first  part  of  the  year.  The  longest  minimum 
incubation  period  was  180  days  and  the  shortest  19  days. 

HATCHING    PERIOD. 

The  eggs  deposited  by  a  female  do  not  all  hatch  at  the  same  time, 
but  approximately  in  the  sequence  in  which  they  are  laid.  The  time 
required  for  all  of  the  eggs  to  hatch  after  hatching  begins  may  be 
called  the  hatching  period.  This  may  be  considered  normal  in 
length  only  when  approximately  ah1  the  eggs  hatch  or  a  goodly 
portion  of  the  first  and  the  last  eggs  deposited  hatch.  Because  of 
the  low  percentage  of  eggs  which  hatched  in  the  case  of  some  of  the 
ticks  the  hatching  periods  of  these  have  no  significance  and  are, 
therefore,  not  considered  in  the  following  table.  The  average  period 
for  different  months  of  the  year  is  seen  in  the  following  table  to  range 
from  10.6  days  for  July,  1907,  to  36  days  for  October  of  the  same 
year.  The  maximum  period  observed  was  49  days  and  the  minimum 
4  days.  The  eggs  of  all  the  ticks  collected  previous  to  October,  1907, 
hatched  in  the  fall  and  those  laid  by  ticks  collected  October  1  did  not 
begin  to  hatch  until  the  following  March,  and  of  course  the  eggs  of 
those  collected  during  November  and  the  succeeding  months  did  not 
begin  to  hatch  until  later,  consequently  no  hatching  periods  were 
obtained  during  the  colder  part  of  the  year.  It  is  therefore  evident 
that  the  maximum  period  observed  is  much  less  than  might  occur 
with  a  slightly  different  winter  season,  or  if  ticks  had  been  collected 
89053°— Bull.  130—11 3 


16 


BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 


on  such  a  date  that  the  hatching  of  the  eggs  would  have  begun  in 
the  fall  and  not  been  completed  until  the  following  spring. 

Hatching  period — Range  and  average  length  of  periods. 

VERTICAL-TUBE  EXPERIMENTS. 


Month  hatching 
began. 

Number 
of  ticks. 

Range  of 
periods. 

Average 
of  periods. 

Month  hatching 
began. 

Number 
of  ticks. 

Range  of 
periods. 

Average 
ofperiods. 

1907. 
July 

14 

Days. 
4  to  17 

Days. 
10  6 

1908. 
March 

6 

Days. 
21  to  31 

Days. 
26 

August      

7 

8  to  16 

13.4 

April           

8 

16  to  27 

23.6 

October 

6 

31  to  49 

36 

May 

11 

12  to  18 

•    14  3 

June. 

14 

12  to  22 

17  2 

HORIZONTAL-TUBE  EXPERIMENTS. 


1907. 
October 

5 

18  to  37 

23.6 

1908. 
March 

31        21  to  24 

22  3 

April      

7  i        10  to  27 

21.3 

May... 

12  '         9  to  21 

15.6 

June 

16  j         5  to  18 

11.4 

LONGEVITY    PERIOD. 

The  longevity  of  the  larvae  depends  on  individual  vitality,  humid- 
ity, and  temperature.  Some  larvae  do  not  have  sufficient  vitality  to 
disengage  themselves  from  the  ruptured  eggshell  and  die  partly  inclosed 
within  it.  This  was  especially  noticeable  in  eggs  laid  during  the 
winter,  so  it  would  seem  that  a  low  temperature  may  affect  the 
vitality  of  unhatched  larvae.  Other  larvae  die  very  soon  after 
emerging.  Cold  prolongs  longevity  because  of  the  fact  that  the 
tick  remains  quiescent,  and  as  a  result  the  body  fluids  and  nourish- 
ment are  conserved.  A  high  relative  humidity  prolongs  longevity 
by  hindering  the  loss  of  body  moisture  by  evaporation  and  also  by 
causing  the  ticks  to  remain  more  quiescent  than  when  the  air  is 
dry.  In  addition  to  these  factors  certain  instincts  of  the  larvae 
promote  longevity.  They  respond  negatively  to  light.  In  sunny 
places  they  collect  on  the  under  or  the  shady  side  of  leaves,  stems, 
and  other  objects,  thus  protecting  themselves  from  the  direct  heat 
of  the  sun.  They  also  manifest  an  interesting  adaptation  in  being 
able  to  detect  the  presence  of  a  possible  host  at  a  distance  of 
several  feet.  This  fact  was  observed  and  verified  many  times  with 
larvae  located  on  plots  outdoors.  Larvae  that  were  quiescent  when 
one  approached  within  3  or  4  feet  of  a  plot,  in  the  course  of  a 
half  to  several  minutes  became  very  active  and  extended  their  front 
legs  upward  in  a  divergent  position,  waving  them  violently  in  an 
evident  attempt  to  seize  onto  a  host.  This  instinct  is  probably 
dependent  on  an  olfactory  sense  resident  in  the  organ  of  Haller 
located  on  the  tarsi  of  the  first  pair  of  legs.  It  may  possibly  be 


THE   LONGEVITY   PERIOD. 


17 


connected  with  a  thermal  sense,  but  this  hardly  seems  probable, 
since  the  reaction  was  found  to  occur  just  as  readily  on  extremely 
warm  days  as  on  cool  days.  The  response  takes  place  more  quickly 
when  one  is  located  on  the  windward  side  of  the  larvae.  .This  instinct 
permits  the  larvae  to  remain  quiescent  without  reducing  their  chances 
for  reaching  a  host.  The  periods  of  inactivity  conserve  the  vitality 
of  the  tick  and  consequently  must  prolong  longevity. 

In  making  observations  on  the  longevity  >  the  date  when  the  larvae 
in  each  tube  began  to  die  and  when  all  of  them  were  dead  was  re- 
corded. In  determining  the  longevity  of  the  larvae  resulting  from 
each  lot  of  eggs,  the  date  when  the  eggs  began  to  hatch,  together  with 
the  two  dates  just  mentioned  above,  were  used,  thus  obtaining  a  min- 
imum and  maximum  longevity  period. 

The  range  of  the  maximum  and  the  minimum  longevity  and  the 
average  of  the  former  for  lots  of  larvae  hatched  during  the  different 
months  of  the  year,  are  given  in  the  following  table: 

Longevity  period — Range  of  maximum  and  minimum  longevity  and  average  of  maximum 

longevity. 


Range  of 

Range  of 

Average 

Range  of   Range  of 

Average 

Month 
hatched. 

Num- 
ber of 
lots. 

mini- 
mum lon- 
gevity 

maxi- 
mum lon- 
gevity 

of  maxi- 
mum lon- 
gevity 

Month 
hatched. 

Num-      mini- 
ber  of  mum  Ion- 
lots,      gevity 

maxi- 
mum lon- 
gevity 

of  maxi- 
mum lon- 
gevity- 

periods. 

periods. 

periods. 

periods. 

periods. 

periods. 

1907. 

Days. 

Days. 

Days. 

1908. 

Days. 

Days. 

Days. 

July  

106 

4  to  39 

7  to  85 

38.6 

March  

24 

5  to  22 

57  to  94 

73.2 

August 

83 

9  to  36 

9  to  192 

84.9 

April 

189 

3  to  63 

19  to  99 

65.1 

September  . 

44 

4  to  35 

9  to  190 

56.2 

May. 

406 

2  to  57 

4  to  103 

62.3 

October  

75 

5  to  163 

30  to  234 

167.4 

June  

380 

4  to  55 

8  to  128 

65.1 

November... 

5 

21  to  70 

33  to  135 

85 

The  eggs  which  hatched  during  July,  August,  and  September  were 
kept  in  tubes  which  were  not  supplied  with  water  other  than  that 
originally  added  to  the  sand.  This  may  account  for  the  rather  low 
averages  for  July  and  September.  It  is  noted  that  the  highest  average 
is  for  the  lots  hatched  during  the  month  of  October,  and  this  month 
also  gave  the  longest  maximum  period;  the  lowest  average  is  for 
July,  which  likewise  gave  the  shortest  maximum  longevity  period. 

TOTAL    TIME    OF    NON PARASITIC    DEVELOPMENT. 

The  period  of  nonparasitic  development  is  the  time  from  the  date 
the  female  drops  until  all  the  resulting  larvae  are  dead.  It  is  of  prime 
importance  from  a  practical  standpoint,  since  it  indicates  the  length  of 
time  animals  must  be  kept  out  of  an  infested  pasture  in  order  for  it  to 
become  tick  free.  A  summary  of  the  data  on  this  period  is  given  in 
the  table  following. 


18  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 

Total  time  from  dropping  of  female  until  all  resulting  larvse  are  dead. 


Date  engorged 
females  were 
collected. 

Number 
of  en- 
gorged, 
females. 

Range  of 
entire-time 
periods. 

Average 
of  pe- 
riods. 

Date  engorged 
females  were 
collected. 

Number 
of  en- 
gorged 
females. 

Range  of 
entire-time 
periods. 

Average 
of  pe- 
riods. 

Junel,  1907.  ... 
Julyl,  1907.   ... 
Aug.  1,  1907.  .. 

7 

7 

Days. 
79  to  100 
82  to  112 
172  to  221 

Days. 
86.9 
101 
199.6 

Dec.  29,  1907,  to 
Jan.  1,1908  
Jan.  29  to  Feb.  4, 

3 

Days. 
181  to  207 

Days. 
196.3 

Aug.  31,  1907 

6 

230  to  272 

250.7 

1908 

7 

156  to  189 

173  1 

Oct.  1,  1907.    ... 
Nov.  1,  1907.   ... 
Nov.  30,  1907  .  .  . 

7 
7 
.      3 

276  to  288 
200  to  253 
187  to  249 

279.6 
232.7 
217 

Feb.  27  to  28,  1908. 
Mar.  26  to  29,  1908. 
Apr.  29,  1908  

2 
9 

14 

143  to  162 
144  to  161 
122  to  173 

152.1 
152.1 
142.8 

In  the  above  table  the  averages  are  seen  to  increase  from  86.9  days 
for  June,  to  279.6  days  for  October,  1907,  and  to  decrease  from  the 
latter  month  for  the  rest  of  the  time.  The  maximum  periods  likewise 
increased  from  100  days  for  June  to  288  days  for  October  and  there- 
after steadily  decreased  each  month  until  March. 

NUMBER   OF   EGGS   LAID   AND   PERCENTAGE   HATCHED. 

The  eggs  laid  by  each  female  (except  in  the  case  of  controls,  which 
are  referred  to  below)  were  counted  when  they  were  removed  and 
before  the}'  were  placed  in  the  incubation  tubes.  And  furthermore, 
after  all  the  larvse  in  each  tube  had  perished,  the  unhatched  eggs 
were  removed  and  counted.  The  purpose  of  this  was  twofold,  first  to 
determine  the  number  of  eggs  laid  by  a  female,  and,  second,  to  calcu- 
late the  percentage  of  eggs  which  hatched.  In  the  case  of  certain  ticks, 
the  eggs  of  which  were  left  uncounted  for  the  purpose  of  serving  as 
controls  on  the  counted  eggs,  it  was  necessary,  in  addition  to  count- 
ing the  unhatched  eggs,  to  count  the  dead  larvse  in  order  to  determine 
the  number  of  eggs  laid.  The  data  obtained  are  given  in  columns  3 
;ind  11,  respectively,  of  Table  1,  Appendix.  A  summary  showing  the 
range  in  the  number  of  eggs  laid  by  each  lot  of  ticks,  the  average  number 
of  eggs  laid  and  per  cent  hatched,  is  presented  in  the  following  table: 

Egg  laying  and  hatching — Total  and  average  number  of  eggs  laid  and  per  cent  hatched. 


Date  ticks  col- 
lected. 

Num- 
ber of 
ticks. 

Eggs  laid. 

Aver- 
age 
eggs 
laid. 

Eggs 
hatched. 

Date  ticks  col- 
lected. 

Num- 
ber of 
ticks. 

Eggs  laid. 

Aver- 
age 

eggs 
laid. 

Eggs 
hatched 

June  1,  1907.  . 
July  1,  1907.  . 
Aug  1,  1907.  .  . 
Aug31,  1907.. 
Oct  1,1907..   . 
Novl,  1907.   . 
Nov  30,  1907  .   . 

7 
6 
7 
7 
4 

Number. 
630-3,095 
1.858-3,820 
1,851-3.683 
2.049-2,809 
960-3,385 
991-2,961 
357-3,  20; 

Number 
1,811 
2,919 
2,  WO 
2,405 
2,563 
2,129 
2,173 

Per  ct. 
73-95 
90-97 
90-98 
57  97 

Dec.  29,  1907,  to 
Jan.  1,1908... 
Jan  29,  to  Feb. 
4,  1908 

4 

7 
2 
9 
9 

Number. 
1,970-4,272 

806-4.276 
2,302-2,925 
2.680-4,559 
3,  246-5,  105 

Number 
3,149 

3,331 

2,614 
3,507 
4,089 

Perct. 
0-35 

14-86 
62-96 
66-97 
33-98 

77-92 
1-7 
0-18 

Feb.  27-28,  1908. 
Mar.  26-29.  1908. 
Apr.  29,  1908.... 

EXPERIMENTS   WITH   HORIZONTAL,  TUBES. 


19 


The  minimum  number  of  eggs  laid  was,  as  the  above  table  indicates, 
357,  and  the  maximum  number  5,105.  The  average  number  ranges 
from  1,811  to  4,089.  The  percentage  of  eggs  hatching  in  the  case  of 
ticks  collected  from  November  1,  1907,  to  January  1,  1908,  ranged 
from  0  to  35,  and  for  the  rest  of  the  time  from  14  to  98. 

In  counting  the  eggs  they  were  placed  on  white  paper  and  arranged 
in  a  long  row  one  egg  deep  and  several  eggs  wide.  In  order  to  injure 
them  as  little  as  possible  and  reduce  the  chances  of  crushing  them, 
small  spatulas  made  of  thin  paper  were  used  in  handling  them.  The 
counting  was  done  with  the  aid  of  a  pocket  lens.  For  the  purpose  of 
determining  whether  the  manipulation  involved  in  counting  the  eggs 
reduced  the  percentage  that  hatched,  two  ticks  in  each  of  the  first  six 
sets  of  experiments  were  selected  as  controls,  their  eggs  not  being 
counted.  The  results  are  given  in  the  following  table: 

Percentage  of  eggs  hatching  from  counted  and  uncounted  lots. 


Date  ticks  collected. 

Num- 
ber 
of 
ticks. 

Eggs  counted 
or  uncounted. 

Per 

cent 
hatched. 

Date  ticks  collected. 

Num- 
ber 
of 
ticks. 

Eggs  counted 
or  uncounted. 

Per 

cent 
hatched. 

1907. 
June  1 

5 

Counted  .  . 

92.  1 

1907. 
Aug.  31  

6 

Counted  .... 

79.5 

Do            ... 

2 

Uncounted. 

84.9 

Do  

1 

Uncounted.. 

97 

July  1 

5 

Counted 

95.3 

Oct.  1 

Counted 

85.5 

Do... 

2 

Uncounted. 

95 

Do  

2 

Uncounted.. 

85.7 

Aug.  1  ... 

5 

Counted  ... 

95.3 

Nov.  1  

-5 

Counted.  .  . 

a4 

Do 

2 

Uncounted. 

95.8 

Do 

2 

Uncounted.. 

Two  of  the  above  averages  for  the  controls  are  less  and  four  are 
more  than  the  corresponding  averages  for  the  counted  eggs.  Disre- 
garding, however,  slight  differences  ranging  from  0.2  to  1.6  per  cent, 
which  have  little  significance,  the  corresponding  average  may  be  said 
to  be  the  same  in  all  except  two  cases.  In  one  of  these  the  average 
for  the  control  is  17.5  per  cent  more  and  in  the  other  7.2  per  cent  less. 
It  seems  safe  to  say  from  the  above  results  that  the  manipulation 
involved  in  counting,  when  done  with  moderate  care,  does  not  appre- 
ciably lower  the  per  cent  of  eggs  hatching,  and  that  this  has  not 
materially  affected  the  percentage  of  eggs  hatched  in  the  course  of  the 
present  experiments. 

EXPERIMENTS   WITH  HORIZONTAL  TUBES. 

The  tubes  used  in  these  experiments  have  already  been  described 
on  page  10  (see  fig.  2).  Those  referred  to  below  as  being  supplied 
with  moisture  were  either  kept  in  a  moist  chamber  or  were  of  the 
type  having  sand  in  one  end.  A  summary  of  the  data  is  given  in  the 
table  following. 


20  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 

Summary  of  the  data  obtained  from  the  experiments  with  horizontal  tubes. 


• 

• 

Total  time 

from  date 

Date  ticks  were 
collected  . 

Preoviposi- 
tion  period. 

Oviposi- 
t  i  on  period. 

Incubation 
period. 

Hatching 
period. 

Longevity 
of  larvae. 

Conditions 
of 
experiment. 

females 
were  col- 
lected to 

death  of 

larvse. 

1907. 

Days. 

Days. 

Days. 

Days. 

Days. 

Days. 

AUK  31  • 

•3 

9  to  17 

30  to  31 

18  to  22 

a  195  to  217 

Moisture 

299  to  250 

Oct.  1  

4 

22  to   37 

165  to  167 

21  to  24 

78  to   92 

do 

247  to  261 

Nov.  1 

9  to  20 

130  to  152 

167 

16 

70 

do 

246 

Nov.  26.. 

20  to  33 

(6) 

do 

Dec.  25  

27  to  33 

74  to  78 

88  to  94 

10  to  25 

62  to    83 

.    do.   .  . 

204 

1908. 

Feb.  3 

29  to  33 

35  to  49 

53  to  59 

20  to  27 

87  to  109 

do 

172  to  194 

Feb.  24  to  Mar.  3.. 

10  to  16 

.50  to  40 

50  to  56 

16  to  24 

71  to  105 

...do... 

131  to  168 

Mar.  23  to25  

5  to   6 

26  to  31 

43  to  48 

9  to  15 

49  to    71 

do.   .. 

103  to  121 

Apr.  29  to  30.. 

5  to   8 

21  to  24 

29  to  32 

5  to  18 

79  to  111 

do 

114  to  147 

May  1 

5  to   9 

15  to  21 

29  to  31 

6  to  10 

15  to    17 

No  moist- 

50 to    53 

ure. 

o  After  all  the  eggs  had  hatched  the  larvae  were  placed  on  vegetation  outdoors. 
6  Only  a  few  eggs  were  laid,  all  of  which  shriveled. 

The  minimum  entire  time  when  the  tubes  were  kept  moist  occurred 
hi  the  case  of  ticks  collected  March  23  to  25,  1908,  and  the  maximum 
with  the  ticks  collected  October  1,  1907.  In  the  case  of  the  vertical 
tubes  the  maximum  entire  time  also  fell  to  the  ticks  collected  October 
1 .  For  the  purpose  of  determining  the  influence  of  moisture  on  the 
duration  of  the  entire  time  some  ticks  collected  May  1,  1908,  were 
kept  in  tubes  which  were  not  supplied  with  moisture.  Other  ticks 
collected  April  29  and  30  were  supplied  with  moisture  as  usual.  The 
difference  in  the  result  is  very  striking,  the  duration  in  the  latter 
case  being  nearly  three  times  as  long  as  in  the  former. 

RECORDS   OBTAINED   FROM  THE   FIELD   PLOTS. 

In  the  indoor  experiments  the  conditions  were  made  to  correspond 
as  nearly  as  possible  with  those  existing  outside.  It  was  evident, 
however,  even  before  the  work  presented  in  this  bulletin  was  taken  up, 
that  this  could  only  be  accomplished  in  a  very  imperfect  manner  and 
that  it  would  be  well  to  conduct  a  parallel  set  of  experiments  outside 
under  natural  conditions  for  the  purpose  of  checking  the  indoor  experi- 
ments. Natural  conditions  are  far  from  being  uniform,  however. 
Even  in  the  same  pasture  a  variety  of  environments  may  be  present 
and  the  duration  of  the  various  periods  in  the  life  history  of  the  tick 
be  quite  different  under  each.  Furthermore,  climatic  conditions  may 
vary  considerably  from  year  to  year  in  the  same  place.  The  impor- 
tant thing,  however,  from  a  practical  standpoint  is  to  determine  the 
environments  that  will  give  maximum  and  minimum  periods.  An 
attempt  was  made  to  obtain  such  periods  by  running  two  sets  of 
field  plots,  one  on  well  drained,  sunny  ground  and  the  other  on  moist, 
partly  shady  ground.  The  character  of  the  plots  and  the  method  of 


INFLUENCE   OF    ENVIRONMENT. 


21 


confining  the  ticks  have  been  described  on  page  11.  In  these  experi- 
ments it  was  not  possible  to  make  notes  on  individual  ticks,  and  con- 
sequently the  data  are  not  as  complete  as  those  of  the  indoor  work. 
The  data  of  economic  importance  are  the  date  the  first  eggs  hatched 
and  the  date  all  the  larvae  were  dead. 

In  four  of  the  plots  located  in  the  sun,  started  June  3,  July  1, 
August  1,  and  August  31,  1907,  the  engorged  ticks  were  destroyed 
by  small  red  ants;0  in  two  started  November  1,  1907,  and  January  31 
to  February  1,  1908,  eggs  were  deposited  but  no  larvae  appeared; 
and  in  three  started  November  26  and  December  16,  1907,  and 
January  1,  1908,  all  the  females  died  without  ovipositing.  In  the 
case  of  plots  located  under  partly  shady  conditions,  in  three  of  them 
started  on  August  31,  October  1,  and  November  1,  1907,  eggs  were 
deposited  but  no  larvae  appeared;  in  two  started  November  26  and 
December  16,  1907,  all  the  females  died  without  depositing  eggs. 

In  all  the  plot  experiments  started  between  November  1,  1907,  and 
January  1, 1908,  inclusive  (see  second  table  below),  no  larvae  appeared, 
either  for  the  reason  that  the  females  succumbed  to  the  severe  weather 
or  that  the  eggs  deposited  failed  to  hatch. 

The  records  of  the  last  three  plots  located  in  the  sunlight  and  in 
the  shade  furnish  an  interesting  comparison  with  regard  to  the 
influence  of  environment  on  the  eggs  and  larvae.  They  are  given  in 
the  following  table: 

Influence  of  environment  on  eggs  and  larvae. 


In  sunlight 

In  shade. 

Date  ticks  were  collected. 

Date  first 
eges 
hatched 

Date  all 
larvse 
wore 
dead. 

Date  ticks  were  collected. 

Date  first 
eggs 
hatched. 

Date  all 
larvae 
were 
dead. 

1908. 
Mar.  1-2 

May     8 

July   31 

1908. 
Feb  28-29        

Mav   18 

Aug.      3 

Mar.  27-28  

Mav   20 

Aug.    8 

Mir.   27  

June    8 

Aug.    23 

Apr.  27  

June    5 

July   28 

Apr.  27          

June  18 

Sept.     5 

Larvae  appeared  from  10  to  19  days  earlier  in  the  sunny  plots  than 
in  the  shady  ones  and  succumbed  3  to  39  days  earlier. 

a  Specimens  of  this  ant  were  sent  to  Prof.  \V.  M.  Wheeler,  of  Harvard  University,  for  identification, and 
found  to  be  one  of  our  small  "Thief  ants,"*  Solcnopsis  m^lrfla  Say,  which  is  common  in  pastures  and  fields, 
where  it  leads  a  subterranean  life  and  feeds  on  larvae  and  pupas  of  other  ants,  on  sprouting  seeds,  dead 
insects,  etc. 


22 


BIOLOGY    OF    THE    TEXAS-FEVER   TICK. 


In  the  following  table  a  comparison  is  made  of  the  results  obtained 
in  the  vertical  tubes  and  in  the  field  plots: 

Comparison  of  records  of  vertical  tubes  and  field  plots,  Auburn,  Ala.,  1907-8. 


Vertical  tubes. 

Field  plots. 

Date  females  were  collected. 

Date  first 
eggs 
hatched. 

Date  all 
larvse 
were 
dead. 

Date  females  were  collected. 

Date  first 
eggs 
hatched. 

Date  all 
larvae 
were 
dead. 

June  1  1907 

July     4 
July   28 
Aug.  27 
Oct.     3 
Mar.  19 
Apr.  17 
May     4 

Apr.  28 
Apr.  27 
Apr.  28 
May   19 
June    4 

Sept.    9 
Oct.    21 
Mar.     9 
May   29 
July   15 
July   11 
Aug.    5 

July  23 
Aug.  11 
Aug.    7 
Sept.    3 
Oct.    19 

June  4,  1907  

July     7 
July   29 
Aug.  30 
(a) 

Aug.    29 
Oct.       8 
Mar.     27 

July  1,  1907         

July  1,  1907  

Aug  1  1907 

Aug.  -1,  1907        

Aug  31,  1907 

Aug.  31,  1907  

Oct.  1,  1907          

Oct.  1,  1907  

Apr.  10 
(a) 

(6) 
(») 
W 
May   14 
May     8 
May   20 
June    5 

June      8 

Nov  1   1907 

Nov.  1,  1907     ... 

Nov.  30  1907 

Nov.  26,  1907  

Dec.  29,  1907  to  Jan.  1,  1908  
Jan  29  to  Feb.  4,  1908 

Dec  16  1907 

Jan.  1,  1908              

Feb.  1  and  2,  1908  

July     22 
Aug.      3 
Aug.    23 
Sept.      5 

Feb  27  and  28  1908 

Feb  28  to  Mar  2,  1908 

Mar.  26  to  29  1908 

Mar  27  and  28,  1908            .   .  . 

Apr.  29,  1908 

Apr.  27,  1908  

No  larvae  appeared. 


&  All  died  without  ovipositing. 


From  the  above  table  it  will  be  noted  that  the  period  from  the  col- 
lection of  the  ticks  to  the  tune  the  first  eggs  hatched  in  the  case  of 
the  indoor  experiments  started  June  1  and  March  26-29  (33  and  54 
days,  respectively)  is  the  same  as  for  the  corresponding  outdoor  ex- 
periments. In  the  case  of  the  remaining  experiments  the  time  is 
shorter  1  to  22  days  for  the  indoor  than  for  the  outdoor  experiments. 
In  all  the  experiments,  except  the  one  begun  August  1 ,  the  time  from 
the  collection  of  the  ticks  to  the  death  of  all  the  larvae  was  longer  by 
from  5  to  42  days  in  the  indoor  than  in  the  corresponding  outdoor 
experiments. 

PER   CENT   OF   FEMALES   OVIPOSITING. 

The  data  obtained  on  this  point  are  not  very  extensive.  In  each  of 
the  lots  of  ticks  collected  on  the  dates  indicated  in  the  second  column 
of  Table  1,  Appendix,  100  per  cent  oviposited  except  in  the  case  of 
the  ticks  collected  November  30  and  December  29,  1907,  to  January 
1,  1908,  of  which  80  and  33  per  cent,  respectively,  oviposited.  Tick 
No.  27,  collected  August  31,  1907,  deposited  but  39  eggs,  none  of 
which  hatched.  This  tick  was  very  probably  abnormal,  but  the  ticks 
that  failed  to  oviposit  were  no  doubt  unfavorably  affected  by  low 
temperature. 

Of  the  ticks  kept  in  the  horizontal  tubes  only  one  failed  to  oviposit. 
This  was  collected  February  3,  1908.  The  majority  of  the  engorged 
females  placed  in  the  plots  outside  during  the  latter  part  of  the  fall 
and  the  winter  of  1907-8  failed  to  oviposit.  They  appeared  to  suc- 
cumb as  a  result  of  low  temperature  and  excessive  moisture.  The 
first  indication  of  abnormality  usually  noticed  was  a  reddish  tinge 


EFFECT  OF   IMMERSION    IN    WATER.  23 

appearing  over  the  Malpighian  tubules,  which  normally  appear  as 
yellow  streaks  through  the  integument  o*f  the  tick.  Then  the  tick 
began  to  swell,  becoming  very  tightly  distended,  tiie  color  became 
dark,  and  finally,  if  not  punctured  by  some  enemy,  the  integument 
ruptured  of  itself  and  a  sanguineous  fluid  issued  from  the  opening. 

EFFECT  OF  IMMERSION  IN  WATER   ON  ENGORGED  FEMALES. 

A  number  of  tests  were  carried  out  to  determine  what  effect  immer- 
sion in  water,  both  before  and  after  the  beginning  of  oviposition,  has 
on  engorged  females.  On  May  1,  1908,  eight  engorged  females  were 
placed  in  separate  wide-mouthed  bottles  and  covered  with  distilled 
water.  All  of  them  died  without  ovipositing. 

The  following  tests  were  made  in  the  Zoological  Laboratory, 
Washington,  D.  C. : 

August  11,  1908,  10  engorged  females  were  collected  and  placed  in  tap  water.  All 
died  without  ovipositing. 

August  13,  9  engorged  females  (collected  August  12)  were  submerged  in  normal  salt 
solution.  All  died  without  ovipositing. 

September  15,  13  engorged  females  (collected  September  10)  that  had  begun 
to  deposit  eggs  were  submerged  in  tap  water.  None  of  them  continued  to  deposit  eggs. 

September  15,  10  engorged  females  (collected  September  10)  that  had  begun  to 
oviposit  were  placed  in  a  Petri  dish  and  half  covered  with  tap  water.  None  of  them 
continued  to  deposit  eggs. 

September  21,  8  engorged  females  (collected  September  15)  that  had  begun  to 
oviposit  were  placed  in  tap  water.  All  died  without  depositing  additional  eggs. 

The  first  effect  of  water  on  engorged  ticks  is  to  cause  them  to 
become  distended,  and  later  the  coloring  matter  of  the  blood  within 
the  body  escapes  and  colors  the  water.  In  some  instances  the  dis- 
tention  of  the  tick  is  so  great  that  its  form  is  almost  spherical.  This 
was  not  so  pronounced  in  normal  salt  solution  as  in  tap  water. 

Hunter  and  Hooker  12  (1907)  found  that  females  submerged  con- 
tinuously in  tap  water  failed  to  oviposit.  In  one  experiment,  how- 
ever, they  found  that  two  out  of  five  ticks  submerged  during  October 
for  91^  hours  deposited  viable  eggs,  but  ticks  submerged  for  115J 
hours  failed  to  deposit  eggs. 

THE  INFLUENCE  OF  MOISTURE  ON  THE  INCUBATION  PERIOD. 

For  the  purpose  of  determining  what  influence  moisture  might  have 
on  the  duration  of  the  incubation  period,  eggs  were  subjected  to 
different  degrees  of  moisture.  The  eggs  used  each  day  had  been 
deposited  by  a  number  of  females  during  the  previous  24  hours. 
Some  of  the  lots  were  placed  in  the  regular  incubation  tubes  and  others 
in  test  tubes  containing  wet  sand.  In  the  former  case  the  eggs  rested 
on  cardboard  that  was  never  more  than  moist,  while  in  the  latter 
case  they  rested  directly  on  wet  sand.  In  one  instance,  referred  to 


24 


BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 


below,  the  eggs  of  a  tick  (No.  138,  Table  1)  were  floated  on  water. 
This  is  considered  a  condition  which  will  furnish  a  maximum  amount 
of  moisture. 

In  determining  the  results  of  the  tests  the  incubation  periods  of 
lots  of  eggs  deposited  on  the  same  date  and  kept  in  regular  incuba- 
tion tubes  were  averaged,  and  the  same  was  done  in  the  case  of  the 
eggs  placed  on  moist  sand.  The  averages  for  lots  deposited  on  12 
days  during  March,  1908,  are  as  follows: 

Average  incubation  periods  of  eggs  under  different  moi:ture  conditions. 


Mar. 
9. 

Mar. 
10. 

Mar. 
11. 

Mar. 
12. 

Mar. 
13. 

Mar. 

14. 

Mar. 
16. 

Mar. 
17. 

Mar. 
18. 

Mar. 
19. 

Mar. 
20. 

Mar. 
24. 

On  cardboard  

Days. 
55 

Days. 
53 

Days. 
54 

Days. 
53 

Days. 
53 

Days. 
52 

Days. 
51 

Days. 
51 

Days. 
53 

Days. 
53 

Days. 
53 

Days. 
51 

On  moist  sand  

51 

52 

£3 

52 

51 

50 

50 

49 

53 

51 

55 

51 

It  is  seen  that  nine  of  the  averages  for  eggs  kept  on  moist  sand  run 
from  one  to  four  days  less,  two  are  the  same  and  one  is  two  days  more 
than  the  corresponding  averages  for  eggs  on  cardboard.  The  mean 
average  for  the  eggs  on  wet  sand  is  approximately  one  day  less  than 
for  those  on  moist  cardboard. 

The  averages  for  169  lots  of  eggs  placed  in  regular  incubation  tubes 
and  101  lots  placed  on  moist  sand  and  on  water  (82  on  moist  sand  and 
19  on  water),  deposited  from  May  6  to  26,  inclusive,  1908,  show  the 
following  result :  Five  of  the  averages  for  eggs  on  moist  sand  and  on 
water  considered  together  are  from  one  to  two  days  less,  thirteen  are 
the  same,  and  three  are  one  day  more  than  the  corresponding  aver- 
ages for  eggs  resting  on  cardboard.  The  average  for  all  the  lots  of 
eggs  on  moist  sand  and  water  is  three-tenths  of  a  day  less  than  for 
those  on  cardboard. 

From  these  tests,  so  far  as  they  go,  it  appears  that  an  abundance  of 
moisture  shortens  the  incubation  period  so  little  that  for  all  practical 
purposes  its  influence  may  be  disregarded. 

PERIODS   IN  THE    PARASITIC   PORTION   OF   DEVELOPMENT. 

There  are  three  stages  in  the  parasitic  portion  of  the  development 
of  the  tick,  viz,  larval,  nymphal,  and  adult.  Until  the  latter  stage  is 
reached  males  and  females  are  not  recognizable  with  certainty.  The 
duration  of  each  of  these  stages  and  the  duration  of  a  single  infestation 
upon  cattle  during  different  portions  of  the  year  are  of  great  practical 
importance.  Upon  the  duration  of  an  infestation  depends  the  time 
animals  must  be  kept  on  tick-free  fields  in  order  to  become  free  from 
ticks. 

Tick-free  animals  were  infested  at  nine  different  times,  as  indicated 
in  column  1,  Table  2,  of  the  Appendix.  It  was  found  that  the  mini- 
mum larval  period  ranged  from  5  to  7  days;  the  minimum  nymphal 


PERIODS   IN   PARASITIC    DEVELOPMENT. 


25 


period  of  females,  9  to  11  days;  the  adult  period,  from  a  minimum  of 
5  to  a  maximum  of  33  days.  The  duration  of  each  infestation,  as 
given  in  the  last  column  of  the  table,  ranged  from  30  to  66  days.  The 
lower  temperature  during  the  fall  and  winter  retarded  the  second 
molt  of  some  of  the  ticks,  prolonging  the  time  that  nymphs  were 
present,  and  increasing  the  duration  of  infestation.  It  seems  pos- 
sible also  that  the  latter  result  may  be  partly  due  to  delayed  fertiliza- 
tion of  the  females,  which  could  readily  obtain  in  case  the  atmospheric 
temperature  wras  such  as  to  reduce  the  activity  of  the  males. 

The  maximum  numbers  in  column  9  of  the  table  (length  of  nymphal 
period)  indicate  the  time  from  the  molting  of  the  first  larva  to  the 
molting  of  the  last  nymph,  and  consequently  represent  the  time  that 
nymphs  were  present  on  the  animal.  This  time  in  all  probability  is 
much  longer  than  the  nymphal  period  of  any  individual  tick. 

A  number  of  days  previous  to  the  second  molt  it  is  possible  to  dis- 
tinguish male  and  female  nymphs  with  a  fair  degree  of  certainty. 
The  former  are  somewhat  smaller  than  the  latter  and  also  differ 
slightly  in  color  and  shape.  The  first  nymphs  to  molt  are  males. 
The  first  female  nymphs  molt  from  one  to  several  days  later.  All  the 
male  nymphs  molt  before  the  last  female  molts  if  they  originally 
attached  to  their  host  on  the  same  date. 

In  the  infestations  made  on  February  29,  April  4,  and  May  23,  after 
the  larvae  had  attached  themselves  a  certain  number  were  marked  and 
observed  from  day  to  day.  The  range  of  the  periods  observed  in 
these  instances  follow. 

Lenyth  of  period*,  and  total  duration  of  para'itic  development. 


Date  larvae  applied. 

Sex. 

Length  of 
larval 
period. 

Length  of 
nymphal 
period. 

Length  of 
adult 
period. 

Duration 
of  para- 
sitic 
period. 

1908. 
Feb.  29  

Females... 
Males  .   . 

Days. 
8  to   9 

7  to    J 
7  to  1 

Days. 
10  to  15 
S  to  10 

Da>/s. 
5  to  13 

Days. 
25  to  34 

Do 

Do... 

(?)... 

A  pr.  4  .  .  . 

Females.. 
Males  . 

(i  to 
5  to    8 

9  to  14 
Mo  12 
9  to  12 
8  to  13 

4  to    9 

25  to  20 

Do 

Mav  2:? 

Fomalps. 

(i    O     '.1 

22  to  25 

"Do  

Males  

Nineteen  larva?  were  marked  in  the  infestation  of  February  2<*. 
One  of  theses  died  previous  to  the  first  molt,  three  disappeared  after 
the  first  molt,  and  one  female  died  three  days  after  the  second  molt. 
The  male  located  beneath  the  latter  left  on  the  following  day.  Twenty- 
six  larvae  of  the  April  infestation  were  marked.  Sixteen  of  these 
disappeared  previous  to  the  first  molt,  one  after  the  first  molt,  and 
one  after  the  second  molt.  In  the  infestation  of  May  23,  23  larva1 
were  marked.  None  disappeared  previous  to  the  first  molt,  four 
disappeared  after  the  first  molt,  none  disappeared  after  the  second 
molt. 


. 

26  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 

There  seems  to  be  no  satisfactory  explanation  for  the  disappearance 
of  the  ticks,  particularly  those  in  the  larval  stage.  Of  course,  ticks 
shortly  after  the  first  and  second  molt  could  easily  be  rubbed  off.  In 
comparing  the  maximum  parasitic  period  in  each  of  the  three  cases 
given  in  the  above  table  with  the  duration  of  the  same  infestations 
given  in  Table  2,  Appendix,  it  is  noted  that  all  the  latter  are  longer. 
The  difference  for  the  infestation  made  February  29  is  10  days;  for 
both  April  4  and  May  23,  12  days.  The  reason  for  tin's  great  differ- 
ence is  not  clear.  It  may  be  due  to  one  or  several  causes,  such  as 
larva?  remaining  on  the  cattle  for  some  days  without  attaching  them- 
selves (this  has  been  noticed  in  several  instances)  or  ticks  after  the 
first  and  second  molt  not  reattaching  immediately  or  becoming 
dislodged  and  later  reaching  the  host  again. 

OBSERVATIONS  ON  THE  MOVEMENT  OF  TICKS  AFTER  THE  FIRST 

AND    SECOND   MOLT. 

Ransom17  (1906,  p.  5)  pointed  out  the  fact  that  Ifargaropus 
annitfatus,  though  remaining  on  the  host,  must  reattach  itself  after 
the  first  and  second  molt  just  as  other  species  do  which  drop  from  their 
host  and  molt  on  the  ground.  Hunter  and  Hooker12  (1907,  p.  29) 
state  that  repeated  careful  observations  show  that  they  do  not  actu- 
ally detach  themselves  at  either  molt.  As  this  question  has  a  more 
or  less  important  bearing  on  the  dissemination  of  ticks,  and  also,  pos- 
sibly, the  transmission  of  Texas  fever,  as  pointed  out  by  Ransom  " 
(1906) ,  some  observations  were  made  along  this  line.  Since  the  cuticle 
shed  at  molting  remains  attached  to  the  skin  of  the  host  for  some  time 
thereafter,  particularly  following  the  second  molt,  it  is  an  easy  matter 
to  determine  whether  the  rostrum  of  the  tick  is  embedded  at  the  origi- 
nal point  of  attachment  or  elsewhere.  The  following  observations 
indicate  that  reattachnient  may  take  place  after  both  the  first  and 
the  second  molt.  Xot  many  specific  observations  were  recorded  with 
regard  to  the  movement  of  young  females,  but  general  observations 
such  as  are  recorded  for  August  7  were  made  at  various  times.  The 
nymphs  referred  to  below  were  marked  early  in  their  larval  stage  by 
clipping  the  hair  surrounding  them  and  were  observed  daily. 

CHANGE    OF    LOCATION    AFTER    THE   FIRST    MOLT. 

January  10,  1908,  one  newly  molted  nyuiph  reattached  6  mm.  from  original  point  of 
attachment  of  larva. 

January  11.  three  newly  molted  nymphs  reattached  3  to  6  mm.  from  original  point. 

May  28,  one  nymph  just  molted  reattached  3  mm.  from  original  point. 

May  29,  one  nymph  just  molted  reattached  8  mm.  from  original  point. 

May  29,  two  nymphs  just  molted  reattached  2  mm.  from  original  point. 

May  29.  four  nymphs  just  molted  reattached  4  mm.  from  original  point. 

May  30,  two  nymphs  just  molted  reattached  2  mm.  from  original  point. 

May  30.  six  nymphs  just  molted  reattached  4  mm.  from  original  point. 


DISTINGUISHING   MALE   AND   FEMALE   NYMPHS.  27 

CHANGE    OF    LOCATION    AFTER    SECOND    MOLT. 

On  July  18,  1907,  a  cow  was  infested  with  larvae.  August  7,  all 
the  nymphs  had  molted.  No  females  could  be  found  that  had  wan- 
dered any  great  distance.  In  many  instances,  however,  females 
were  found  located  a  fraction  of  a  millimeter  to  1  mm.  posterior 
and  several  millimeters  to  one  side  of  the  place  where  previously 
attached. 

In  the  case  of  a  cow  infested  August  17,  1907,  on  September  4  a 
newly  molted  female  was  observed  attached  3  mm.  to  one  side  of  its 
nymphal  skin. 

In  the  case  of  a  cow  infested  November  19,  an  unattached  newly 
molted  female  was  observed  December  19.  She  was  in  the  hair  just 
above  a  male  which  was  attached  beneath  a  nymphal  skin.  On 
December  20  the  female  was  found  attached  near  the  male. 

EARLY  DISTINGUISHING  OF  FEMALE  NYMPHS  BY  MALES. 

Some  interesting  observations  were  made  which  show  how  early 
the  male  tick  may  distinguish  a  nymph  as  a  female  and  locate  beneath 
it.  On  November  19,  1907,  a  cow  was  infested  with  larvae.  Novem- 
ber 28,  three  males  belonging  to  a  previous  infestation  were  found  on 
the  right  side  of  the  dewlap,  and  on  November  29  and  December  2 
two  more  were  found,  making  five  in  all.  On  the  latter  date  two  of 
them  were  located  beneath  nymphs,  and  on  December  3  and  4  two  more 
located  themselves  beneath  nymphs.  December  5  the  first  male 
nymphs  of  the  new  infestation  molted.  They  \vere  located  on  the 
posterior  part  of  the  body.  December  6  the  male  of  the  previous  in- 
festation that  had  not  sought  a  nymph  had  disappeared  and  a  male 
was  found  beneath  a  nymph  on  the  opposite  side  of  the  dewlap. 
This  was  very  likely  the  male  of  the  previous  infestation  which  had 
disappeared  from  its  former  location,  as  none  of  the  nymphs  of  the 
new  infestation  had  molted  on  this  region  of  the  body.  The  nymphs 
selected  by  the  five  males  molted  from  December  9  to  16  and  proved 
to  be  females.  As  observed  in  this  case,  therefore,  female  nymphs 
were  sought  out  by  males  13  to  17  days  after  the  former  had  been 
placed  on  a  cow  as  larvae,  and  3  to  7  days  or  more  before  they  molted 
the  second  time. 

EXPERIMENTS   IN   TRANSFERRING  TICKS    ON   CATTLE. 

The  following  experiments  were  undertaken  for  the  purpose  of 
determining  whether  ticks  which  have  accidentally  dropped  to  the 
ground  after  molting  or  have  been  dislodged  in  some  manner  will 
reattach  and  develop,  provided  they  reach  a  host.  Ransom  n  (1906) 
showed  that  ticks  removed  shortly  after  the  first  and  second  molt, 
or  just  previous  to  the  second  molt,  and  permitted  to  molt  in  the 


28  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 

laboratory  will  reattach  themselves.  Hunter  and  Hooker  12  (1907), 
after  repeated  attempts,  succeeded  in  getting  two  ticks  to  reattach 
One  was  a  female  one-half  engorged  and  the  other  an  adult  which 
molted  in  the  laboratory.  The  former  remained  attached  six  days 
and  then  released  its  hold,  although  not  fully  engorged.  It  deposited 
several  hundred  eggs,  which  failed  to  hatch.  The  failure  to  hatch  was 
not  attributed  to  the  reattachment  of  the  tick. 

Experiment  No.  1. — December  7,  1907,  a  female  recently  molted  was  removed  and 
placed  on  the  dewlap.  December  8,  female  had  taken  hold.  December  13,  female 
was  still  present.  No  further  record. 

Experiment  No.  2. — December  8,  a  recently  molted  female  was  removed  and  placed 
on  the  outside  of  the  left  ear.  December  9,  tick  had  disappeared. 

Experiment  No.  3. — December  9,  a  female  was  removed  and  placed  on  the  median 
line  between  the  shoulders.  December  10,  female  had  taken  hold.  A  male  was  placed 
with  it.  December  11,  male  had  disappeared.  December  13,  a  male  had  located 
beneath  the  female.  December  14,  male  had  disappeared.  December  17,  female  was 
shriveled. 

Experiment  No.  4-— December  14,  removed  a  female  one-sixth  grown  and  placed  it 
on  the  median  line  between  the  shoulders.  December  15,  female  had  disappeared. 

Experiment  No.  5. — January  22,  1908,  removed  four  females  recently  molted  and 
placed  them  on  the  escutcheon  of  a  cow  free  from  ticks.  January  23,  two  of  the  ticks 
had  attached  themselves.  The  others  had  disappeared.  January  25,  one  tick  had 
disappeared.  February  14, 'the  remaining  tick  dropped  from  host,  but  died  without 
depositing  eggs. 

Experiment  No.  6. — January  24,  transferred  two  young  females  to  a  new  host. 
January  25,  ticks  had  disappeared. 

Experiment  No.  7. — January  27,  transferred  three  females  just  molted  to  a  cow. 
They  were  removed  as  nymphs  January  25  and  molted  January  27.  They  were  placed 
on  the  escutcheon  and  in  about  half  an  hour  had  apparently  attached  themselves. 
January  28,  ticks  had  disappeared. 

Experiment  No.  8. — January  30,  placed  a  female  just  molted  on  a  cow.  Female  was 
removed  as  a  nymph  January  25  and  kept  in  the  laboratory.  Molted  January  30. 
January  31,  tick  still  present.  February  2,  tick  had  disappeared. 

Experiment  No.  9. — February  23,  placed  a  female,  which  molted  in  the  laboratory 
February  22,  on  the  escutcheon  of  a  tick-free  cow.  February  24,  female  had  dis- 
appeared. 

Experiment  No.  10. — February  26,  placed  two  females,  which  molted  in  the  labora- 
tory February  24  and  25,  on  the  escutcheon  of  a  cow.  At  the  end  of  30  minutes  they 
had  apparently  attached  themselves.  February  27,  ticks  had  disappeared. 

Experiment  No.  11. — March  2,  a  female  which  was  removed  February  24  and  molted 
in  the  laboratory  March  1  was  placed  on  a  cow.  At  the  end  of  three  hours  it  was 
observed  attached  to  the  udder.  March  4,  tick  had  disappeared. 

Experiment  No.  12. — March  5,  placed  two  females  on  the  dewlap  of  a  cow.  They 
were  removed  as  nymphs  on  February  24  and  March  2  and  molted  in  the  laboratory 
March  5.  March  6,  ticks  had  disappeared. 

Experiment  No.  13.- — March  7,  placed  two  females  on  the  escutcheon  of  a  cow. 
They  had  been  removed  as  nymphs  March  2  and  4  and  molted  March  7.  March  8, 
ticks  had  disappeared. 

Experiment  No.  14. — March  9,  placed  a  female,  which  was  removed  as  a  nymph 
March  2  and  molted  March  8,  on  the  left  shoulder  of  a  cow.  March  10,  tick  had  dis- 
appeared. 


BEARING   UNFERTILIZED    FEMALES.  29 

Experiment  No.  15. — March  18,  placed  three  females  on  the  flank  of  a  cow.  They 
had  been  removed  as  nymphs  March  17  and  molted  March  18.  They  had  disappeared 
half  an  hour  later,  apparently  having  been  licked  off. 

Experiment  No.  16. — March  19,  three  females,  collected  as  nymphs  March  17  and 
molted  March  19,  were  placed  on  the  neck  of  a  cow.  March  20,  one  tick  waa  attached 
to  the  shoulder,  one  to  the  dewlap,  and  the  other  had  disappeared.  March  21,  the  tick 
on  the  shoulder  had  disappeared.  March  29,  tick  was  about  one-third  engorged. 
April  1,  tick  was  dead. 

Experiment  No.  17. — March  26,  placed  a  female,  which  was  collected  as  a  nymph 
March  17  and  molted  March  26,  on  the  neck  of  a  cow.  The  tick  disappeared  the  same 
day. 

Experiment  No.  18. — April  1,  two  females,  which  were  collected  as  nymphs  March 
17  and  molted  March  31  and  April  1,  were  placed  on  the  neck  of  a  cow.  April  2,  ticks 
had  disappeared. 

Experiment  No.  19.— April  2,  placed  a  female,  which  was  collected  as  a  nymph  from  a 
horse  and  molted  April  2,  on  neck  of  a  cow.  April  4,  tick  was  present.  April  5,  tick 
had  disappeared. 

In  the  above  experiments  32  ticks,  shortly  after  the  second  molt, 
were  applied  with  special  care.  Twenty-four  of  them  disappeared 
either  on  the  same  or  the  following  day  and  8  remained  attached  for 
periods  ranging  from  2  to  23  days.  The  one  that  was  attached  for 
23  days  (Experiment  No.  5)  became  nearly  engorged  and  dropped, 
but  failed  to  deposit  eggs.  None  of  the  remainder  approached 
engorgement.  Two  of  them  died  attached  to  the  host,  while  the  rest 
simply  dropped  off. 

Unfortunately  no  tests  were  made  with  ticks  in  the  stage  just  after 
the  first  molt.  It  seems  likely  that  ticks  in  this  stage,  on  account  of 
their  smaller  size,  would  attach  themselves  with  much  greater  facility 
and  develop  to  maturity  more  frequently  than  do  adult  females. 
A  female  one-sixth  grown,  mentioned  in  Experiment  No.  4,  failed  to 
attach. 

In  addition  to  this  test,  on  April  13,  1908,  five  females,  which  had 
just  been  collected  from  a  horse,  ranging  in  size  from  just  after  the 
second  molt  to  one-sixth  grown,  were  placed  on  a  cow,  but  none  of 
them  became  attached. 

EXPERIMENTS   ON   REARING   UNFERTILIZED   FEMALES. 

It  is  next  to  impossible  to  arrange  an  experiment  for  rearing 
unfertilized  females  that  entirely  excludes  the  possibility  of  error. 
Perhaps  the  most  reliable  method  would  be  to  obtain  an  animal  free 
of  all  ticks  and  infest  it  with  females  that  have  molted  in  the 
laboratory.  Unfortunately  all  the  experiments  described  in  the 
preceding  section  to  rear  females  to  engorgement  by  this  method  were 
unsuccessful  except  in  the  case  of  one  female  transferred  to  a  new  host 
shortly  after  molting  (see  Experiment  No.  5,  p.  28),  which,  however, 
failed  to  deposit  eggs.  In  some  additional  work  attempted  along 
this  line  a  different  method  was  used.  An  animal  free  of  ticks  was 


30  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 

infested  with  a  small  number  of  larvae.  The  male  nymphs  were 
removed  as  soon  as  the  sexes  could  be  distinguished.  The  animal 
was  examined  twice  a  day,  but  in  spite  of  the  greatest  care  some  males 
escaped  and  were  occasionally  found  beneath  females.  In  such  cases 
both  were  removed  and  destroyed.  The  females  kept  under  obser- 
vation were  examined  as  a  rule  both  morning  and  evening.  It  can 
not  definitely  be  asserted  that  they  were  unfertilized,  since  the  method 
used  did  not  exclude  this  possibility,  but  at  no  time  were  males  found 
beneath  them.  The- results,  while  they  prove  nothing  with  regard 
to  undoubtedly  unfertilized  females,  show  at  least  two  interesting 
things  which  will  be  mentioned  below. 

April  19,  1908,  a  cow  was  infested  with  larvae.  About  one  hundred  were  placed  on 
the  right  side  of  the  neck  and  the  same  number  on  the  inside  of  the  left  thigh.  All  the 
nymphs  that,  so  far  as  could  be  judged,  were  males  were  removed  as  soon  as  possible. 
On  May  12  a  female  with  a  male  beneath  her  was  removed.  Both  were  destroyed. 
May  22  a  female  dropped.  It  was  not  as  large  as  an  ordinary  engorged  female. 
Length  8  mm.,  width  5  mm.,  very  thin  in  the  dorso- ventral  axis,  color  yellow.  This 
tick  began  to  oviposit  May  27.  The  eggs  developed  white  spots  but  failed  to  hatch. 
On  May  24  one  female  dropped  but  could  not  be  found.  On  May  26  another  female 
dropped  and  was  lost.  No  more  ticks  were  collected  from  this  animal. 

A  cow  was  infested  May  27.  Larvae  were  placed  on  the  escutcheon  and  right  side 
of  neck.  Male  nymphs  were  removed  as  soon  as  possible  but  some  males  escaped. 

June  20,  removed  a  fully  engorged  female  beneath  which  a  male  was  never  seen. 
Oviposition  began  June  24.  Eggs  hatched. 

June  22,  removed  a  fully  engorged  female  beneath  which  a  male  was  never  seen. 
Oviposition  began  June  24.  Eggs  hatched. 

June  26,  a  fully  engorged  female  dropped.  A  male  was  never  observed  with  it. 
Oviposition  began  June  29  and  eggs  hatched . 

June  26-27,  night,  a  female  nearly  engorged  dropped.  A  male  was  never  noticed 
with  her.  Oviposition  began  June  29  and  the  eggs  hatched . 

June  29,  removed  two  females  nearly  engorged;  males  were  never  seen  with  them. 
Both  oviposited  and  though  the  white  urinary  vesicle  appeared  in  the.  eggs  not  more 
than  half  a  dozen  hatched. 

July  18,  removed  a  female  two-thirds  engorged.     Eggs  did  not  hatch. 

July  24,  removed  the  last  two  females.  They  were  not  fully  engorged  and  had 
grown  very  slowly.  One  died  without  ovipositing  and  the  other  laid  a  normal  number 
of  eggs  but  these  failed  to  hatch. 

From  the  above  observations  it  can  be  concluded  that  females 
which  at  least  have  not  had  males  with  them  for  any  length  of  time 
(and  possibly  not  at  all)  will  as  a  rule  deposit  a  normal  number  of 
viable  eggs.  It  should  be  mentioned  that  Morgan  13  (1899,  p.  129) 
records  observations  on  a  presumably  unfertilized  female  which  laid 
viable  eggs.  Another  thing  indicated  is  that  the  parasitic  period 
may  be  prolonged  by  excluding  males,  and  in  consequence  of  this 
the  period  that  an  animal  remains  infested  is  increased.  In  the  case 
of  the  animal  infested  May  27,  the  duration  of  the  infestation  was  58 
days  or  about  one  and  a  half  times  as  long  as  occurred  in  the  case  of 
a  cow  infested  May  23  of  the  same  year.  That  the  adult  period  is  not 


THE    OCCURRENCE   OF    DEAD   TICKS.  31 

always  prolonged,  however,  is  indicated  by  the  experiment  with  a 
newly  molted  female  that  was  transferred  to  an  animal  January  22 
and  dropped  February  14,  after  an  adult  period  of  23  days  (Experi- 
ment No.  5,  p.  28).  This  comes  within  the  range  (8  to  33  days)  of 
the  adult  period  obtained  at  about  the  same  time  on  another  animal 
(Table  2,  Appendix) .  The  tick  obtained  from  the  cow  infested  April 
19  remained  on  the  cow  33  days  and  the  one  that  dropped  May  26, 
37  days,  which  is  5  days  and  1  day  less,  respectively,  than  the  dura- 
tion of  an  infestation  of  another  animal  made  April  4. 

THE    OCCURRENCE    OF   DEAD   TICKS    ON   CATTLE. 

Dead  ticks  are  frequently  found  attached  to  cattle.  In  some 
instances,  especially  in  the  case  of  partially  or  fully  engorged  females, 
they  have  clearly  been  crushed  by  the  host  rubbing  or  coming  in 
contact  with  fences,  buildings,  etc.  In  man}'  instances,  however, 
dead  ticks  are  found  that  have  not  been  injured  in  this  manner,  and  a 
microscopical  examination  of  a  number  of  such  ticks  failed  to  reveal 
a  fungus  or  anything  that  might  have  caused  death. 

In  observations  made  from  November  6,  1907,  to  March.  26,  1908, 
on  animals  used  in  the  life-history  studies,  dead  nymphs  were  noticed 
most  frequently,  females  next,  and  only  one  male  and  one  larva  were 
found  dead.  The  dead  ticks  did  not  occur  uniformly  over  the  entire 
body.  The  greater  number  were  foil  ml  on  the  neck  and  shoulders, 
and  then  in  the  order  named,  on  the  tail,  dewlap,  vulva,  and  flank. 

The  following  is  a  record  of  dead  ticks  found  on  cattle: 

November  6,  1907,  one  nymph  on  tail.  November  10,  one  nymph  on  tail.  Decem- 
ber 6,  one  nymph  on  side  of  neck.  December  14,  one  nymph  on  side  of  neck.  De- 
cember 30,  one  nymph  on  dewlap.  February  1,  1908,  one  nymph  near  vulva.  Feb- 
ruary 14,  one  nymph  on  neck.  February  20,  female  one-sixth  grown,  on  shoulder. 
February  21,  three  nymphs  on  neck.  February  22,  one  female  on  neck.  February  23, 
two  nymphs  on  neck.  February  26,  female,  nearly  grown,  at  root  of  tail.  February 
27,  two  nymphs  on  neck.  March  5,  one  larva  on  shoulder.  March  17,  one  nymph  on 
neck.  March  19,  one  nymph  on  shoulder.  March  19,  one  male  on  neck.  March  24, 
one  nymph  on  dewlap.  March  25,  a  female  attached  near  the  edge  of  a  pustule  on  the 
right  flank.  March  26,  female  about  one-third  down  on  tail.  She  had  a  male  beneath 
her. 

HOST   RELATIONS    OF   THE    CATTLE   TICK. 

Ixodes  annulatus  (—  M.  annulatus)  was  first  reported  by  Say  (1821) 
from  a  deer  (Cervus  virginianus—Cariacus  amcncanus]  from  east 
Florida.  There  are  specimens  in  the  collection  of  the  zoological 
laboratory  of  this  bureau  collected  from  a  deer  in  Santa  Barbara 
County,  Cal.,  and  at  San  Simeon,  San  Luis  Obispo  County,  Cal. 
Besides  cattle,  this  tick  occurs  frequently  on  horses  and  mules  running 
on  infested  pastures.  Hunter11  (1907)  reports  the  tick  on  sheep  (Oris 
aries)  in  Jackson,  Calhoun,  and  Victoria  Counties,  Tex.  During  the 
summer  and  fall  of  1907,  in  the  course  of  the  work  upon  which  the 


32  BIOLOGY   OF    THE    TEXAS-FEVER   TICK. 

present  paper  is  based  the  cattle  tick  was  collected  from  sheep  at 
the  Alabama  Experiment  Station,  Auburn,  and  also  in  Wilcox  County, 
Ala.  There  are  specimens  in  the  zoological  laboratory  of  this  bureau 
from  a  goat  (Capra  Tiircus)  collected  in  Elmore  County,  Ala. 

Ransom  17  (1906)  in  an  account  of  an  experimental  infestation  of 
a  cat  reports  ticks  present  in  the  larval  and  nymphal  stage.  Only 
one  nymph  molted — a  female  that  never  became  engorged.  Males 
and  females  that  molted  in  the  laboratory  attached  themselves  to 
a  tame  rabbit,  but  the  females  failed  to  develop  further.  Din- 
widdie  9  (1908)  reared  experimentally  the  cattle  tick  on  a  dog.  The 
females  failed  to  reach  the  usual  size  but  deposited  viable  eggs. 

In  the  course  of  the  investigations  reported  in  the  present  paper 
larvae  were  applied  to  the  rabbit,  cat,  dog,  and  sheep. 

INFESTATION    EXPERIMENTS    ON    RABBITS. 

Experiment  No.  1. — A  white  rabbit  was  infested  July  25,  1907,  with  larvae  hatched 
June  28-July  13.  July  26,  one  larva  attached  to  ear;  four  or  five  found  crawlin'g 
about  through  the  hair.  July  27,  five  larvse  found  attached  to  body  and  ears.  July 
30.  one  of  the  larvae  found  on  ear  continues  to  develop;  one  on  the  body  dead,  having 
developed  very  little.  August  1,  one  larva  in  the  act  of  molting.  August  6,  a  nymph 
found  on  ear.  August  12,  nymph  on  ear  still  present,  but  not  developing.  A  male 
nymph  had  molted.  August  17,  no  ticks  could  be  found. 

Experiment  No.  2. — August  19,  1907,  white  rabbit  infested  with  larvae  hatched 
June  28-July  13.  August  20,  many  larvae  found  attached  to  the  ears.  August  26, 
one  larva  found  on  tip  of  right  ear.  August  29,  one  nymph  found  on  inside  of  the  tip 
of  the  right  ear.  September  4,  nymph  still  present.  September  9  and  16,  no  ticks 
could  be  found. 

Experiment  No.  3. — September  25,  1907,  white  rabbit  infested  with  larvae,  the 
progeny  of  ticks  collected  August  16  from  a  horse.  October  8.  no  ticks  could  be 
found. 

Experiment  No.  4- — December  12,  1907,  placed  two  females  recently  molted  on 
a  white  rabbit.  The  rabbit  was  also  infested  with  larvae.  December  13,  no  ticks 
present.  December  14,  placed  two  more  females  recently  molted  on  the  rabbit. 
December  15,  the  two  transplanted  females  have  disappeared.  December  19,  30, 
and  January  17,  1908,  no  ticks  present. 

Experiment  No.  5. — January  20,  1908,  a  black  and  white  rabbit  infested  with  larvae. 
Examinations  made  January  22.  30,  and  February  11  revealed  no  ticks. 

Experiment  No.  6.— March  2,  1908,  a  black  and  white  rabbit  infested  with  larvae. 
March  4,  three  dead  larvae  on  the  ears — two  attached  and  one  in  the  hair.  Two  live 
larvae  seen  crawling  over  the  hair  of  the  head  and  face.  March  13,  two  dead  larvae 
noted.  Neither  showed  any  development.  March  27,  no  ticks  present. 

Experiment  No.  7. — June  18,  1908,  white  rabbit  infested  with  larvae.  July  2,  four 
nymphs  and  a  female  just  molted  located  on  the  ears.  July  6,  female  had  disappeared. 
All  the  nymphs  were  dead. 

Experiment  No.  8. — June  18,  1908,  a  white  and  gray  rabbit  was  infested  with  larvae. 
July  11,  three  dead  nymphs  were  found  on  ears,  one  in  stage  of  molting.  A  nymphal 
skin  was  attached  to  the  right  ear.  but  the  tick  that  had  issued  from  it  could  not  be 
found. 

It  is  evident  from  the  above  experiments  that  the  rabbit  is  not 
an  appropriate  host  for  the  cattle  tick.  Out  of  a  large  number  of 


HOST   RELATIONS   OF   THE   CATTLE   TICK.  33 

larvae  placed  on  each  rabbit  none  in  sonic  cases,  in  others  compara- 
tively few,  attached  themselves.  It  also  appears  that  adults  either 
resulting  from  nymphs  dislodged  from  cattle,  or  themselves  dislodged 
from  cattle,  would  not  be  likely  to  attach  to  a  rabbit  in  case  an 
opportunity  were  presented. 

Larvae,  nymphs,  and  adults  (males  and  females)  were  reared  on 
rabbits,  but  in  no  case  did  females  develop  beyond  the  second  molt. 
The  blood  of  the  rabbit,  or  something  else  peculiar  to  the  animal, 
is  unfavorable  to  the  tick.  This  is  evidenced  by  the  fact  that  many 
of  the  larvae  and  nymphs  die  without  reaching  the  point  of  molting. 
It  seems  possible,  however,  that  in  rare  cases  females  might  attain 
partial  or  complete  engorgement  on  rabbits,  but  the  chances  against 
the  tick  on  the  rabbit  are  so  great  that  such  a  possibility  seems 
negligible  for  all  practical  purposes. 

In  the  above  experiments  only  tame  rabbits  were  used.  An 
attempt  was  made  to  raise  a  wild  rabbit  in  captivity  for  use  in  the 
experiments,  but  this  was  unsuccessful.  A  number  of  wild  rabbits 
obtained  in  the  vicinity  of  Auburn,  Ala.,  and  in  Wilcox  County, 
Ala.,  were  examined  for  cattle  ticks  with  negative  results.0  Farmers 
and  stockmen  in  the  South  frequently  state  that  they  have  found 
cattle  ticks  on  wild  rabbits,  but  observation  and  experiment  tend 
to  show  that  these  must  be  other  species  of  ticks,  probably  most 
commonly  Ilxmaphysalls  leporis-palustris. 

INFESTATION    EXPERIMENTS    ON    A    CAT. 

Experiment  No.  9. — July  24,  1907,  a  kitten  was  infested  with  larvae  hatched  June 
28-July  13.  July  25,  one  larva  was  found  attached  to  the  inside  of  thigh.  July  26, 
larva  on  thigh  still  present  and  another  located  on  left  ear.  July  29,  larvae  still  present. 
July  31,  larva  on  thigh  molted.  August  6.  nymph  still  present.  August  10,  nymph 
disappeared.  August  17,  no  ticks  found. 

Experiment  No.  10. — August  19.  kitten  infested  with  larvae  hatched  June  28-July  13. 
August  20,  a  few  larvae  attached  to  the  ears  and  abdomen.  Examinations  on  August 
26,  30,  and  September  4  revealed  no  ticks. 

Experiment  No.  11. — A  third  infestation  of  the  kitten  was  made  December  12  without 
result. 

It  appears  so  far  as  the  above  experiments  go  that  the  cat  is  even 
a  less  favorable  host  than  the  rabbit. 

INFESTATION    EXPERIMENT    ON    A    DOG. 

Experiment  No.  12. — A  dog  was  infested  August  30,  1907,  without  result. 

INFESTATION    EXPERIMENTS    ON    SHEEP. 

Seven  attempts  were  made  at  various  times  to  infest  sheep  with  the 
tick,  and  six  of  these  were  unsuccessful.  In  the  case  of  one  of  the 
unsuccessful  attempts,  made  May  15,  1908,  the  animal  was  shorn  on 

a  In  July,  1910,  20  cottontails  and  6  jack  rabbits  were  shot  on  the  Rincon  Ranch.  Gregory .  Tex.,  and 
examined  for  cattle  ticks,  with  negative  results.  The  rabbit  tick  (Ilsrmaphyaalis  leporis-palu.*/ris)  was 
found  on  both  jacks  and  cottontails,  but  was  much  more  abundant  on  the  former. 


34  BIOLOGY    OF    THE    TEXAS-FEVER   TICK. 

the  previous  day  to  allow  the  larvae  to  reach  the  skin  with  greater  ease. 
In  another,  made  September  25,  the  progeny  of  females  matured  on  a 
horse  were  used. 

The  record  of  the  one  infestation  that  was  partially  successful  is  as 
follows : 

July  24,  1907,  a  sheep  was  infested  with  larvae  hatched  June  28-July  13.  July  27, 
several  larvae  were  attached  to  the  ventral  surface  of  the  body.  August  10,  one  female 
tick  a  little  over  one-fourth  grown  was  located  on  the»outside  of  the  left  ear.  August  12, 
tick  had  disappeared.  There  was  a  bloodstain  where  the  tick  had  been  attached,  sug- 
gesting that  it  may  have  been  crushed. 

In  two  of  the  negative  experiments  dead  larvae  were  found  in  the 
wool  and  also  attached  to  the  skin.  At  each  infestation  thousands  of 
larvae  were  applied,  and,  in  most  cases,  to  all  parts  of  the  body.  The 
very  small  number  of  larvae  that  attached  themselves  indicates  that 
sheep  are  not  favorable  hosts  for  the  tick.  The  presence  of  dead 
larvae  seems  to  indicate  that  there  are  conditions  on  the  surface  of  the 
body  or  substances  in  the  skin  and  blood  unfavorable  to  the  tick. 

THE    NATURAL    OCCURRENCE    OF   THE    CATTLE    TICK    ON    SHEEP. 

In  order  to  determine  to  what  extent,  under  natural  conditions, 
sheep  serve  as  hosts  for  the  cattle  tick,  some  field  experiments  were 
carried  out,  and  in  addition  to  this  a  considerable  number  of  sheep 
running  on  infested  pastures  were  inspected. 

In  one  of  the  field  experiments  six  native  sheep  were  allowed  to  run 
with  two  cattle  on  an  infested  pasture  containing  about  4  acres,  from 
July  18,  1907,  to  November  6  of  the  same  year.  No  ticks  were  found 
at  any  time  on  the  sheep,  although  the  two  cattle  carried  a  moderate 
infestation  until  shortly  before  the  close  of  the  experiment,  when  the 
weather  had  become  cool. 

In  a  second  experiment  six  native  sheep  were  allowed  to  run  alone 
on  an  infested  pasture  similar  to  the  above  from  July  18  to  November 
26,  1907.  A  ram  and  ewe  were  carefully  examined  on  September  7. 
The  ewe  was  free  of  ticks  and  the  ram  had  six  ticks,  as  follows :  One 
engorged  female,  two  males,  and  a  dead  female  shortly  after  the  sec- 
ond molt,  on  the  neck,  one  female  about  one-eighth  grown  on  the 
outside  of  the  upper  portion  of  one  fore  leg,  and  another  female  one- 
sixth  grown  on  the  abdomen  where  hair  was  present.  The  engorged 
female  was  unattached,  but  entangled  in  the  wool  in  such  a  manner 
that  it  could  not  drop  from  the  host.  It  had  been  in  this  condition 
for  several  days,  as  it  had  begun  to  oviposit.  All  of  the  sheep  were 
examined  with  great  care  on  November  26,  when  the  experiment  was 
closed,  and  were  found  free  of  ticks. 

Through  the  kindness  of  Prof.  D.  T.  Gray  it  was  possible  to  inspect 
sheep  for  cattle  ticks  at  the  experiment  station  at  Auburn.  The 
sheep  were  running  on  an  infested  pasture,  mostly  woodland,  along 
with  a  few  cattle. 


HOST  RELATIONS   OF   THE    CATTLE   TICK.  35 

On  September  26,  1907,  five  sheep  were  subjected  to  a  hand  inspec- 
tion and  two  were  found  infested.  A  native  ewe  had  a  female  tick 
on  its  ear;  and  a  Dorset  ram  carried  a  number  of  males,  females,  and 
one  nymph.  Some  of  the  males  were  dead.  They  were  unattached 
and  located  in  the  wool.  One  female  just  after  the  second  molt  had 
a  male  beneath  her.  The  largest  female  collected  was  possibly  a  little 
more  than  one-sixth  grown.  Most  of  the  ticks  were  located  on  hairy 
parts  of  the  body,  especially  the  legs.  On  one  native  ewe  two  dead 
larvae  were  found. 

On  October  3,  12  native  ewes  and  the  Dorset  ram  in  the  above  flock 
were  inspected.  The  ewes  were  free  (one  harbored  a  dead  larva)  and 
the  Dorset  ram  harbored  two  males.  The  skin  of  7  of  the  ewes 
was  oily,  that  of  the  other  5  was  moderately  oily,  and  that  of  the 
Dorset  ram  was  not  oily.  On  October  12  the  ram  was  inspected 
again.  The  wool  and  skin  were  very  free  from  oil.  Ticks  were  found 
as  follows:  Two  females  one-third  and  one-sixth  grown  with  males 
beneath  them  on  one  hind  leg  a  short  distance  above  the  hoof;  a  fe- 
male just  after  the  second  molt  on  the  posterior  surface  of  the  thigh 
with  a  male  situated  some  little  distance  below  it;  a  female  one- 
fourth  grown  with  a  male,  located  on  the  scrotum;  and  a  dead  male  in 
the  wool.  On  October  14  one  of  the  females  on  the  leg  and  the  one  on 
the  scrotum  had  become  nearly  engorged  and  were  removed.  The 
former  was  crushed  in  removing.  On  October  16  another  female 
nearly  engorged  was  removed  from  the  hind  leg.  Both  of  the  uninjured 
ticks  laid  viable  eggs. 

On  November  12  to  13,  1907,  36  sheep,  principally  grade  South- 
downs,  in  Wilcox  County,  Ala.,  were  subjected  to  a  careful  hand 
inspection.  These  sheep  had  been  running  continuously  during  the 
summer  and  fall  with  240  head  of  cattle  that  were  grossly  infested 
with  ticks  prior  to  October  24,  when  they  had  been  dipped.  All  the 
sheep  were  in  high  flesh.  All  but  one  of  them  were  free  from  ticks. 
Thirteen  of  the  sheep  had  wool  that  was  not  oily;  14  had  moderately 
oily  wool;  and  S  had  oily  wool.  The  one  infested,  a  ram  with 
moderately  oily  wool,  had  a  female  tick  one-half  grown  on  the  hairy 
portion  of  the  scrotum. 

On  November  14  to  18  a  flock  of  125  sheep  in  the  same  locality  was 
inspected.  They  had  been  running  continuously  during  the  summer 
ami  fall  in  a  pasture  of  several  hundred  acres  with  over  200  cattle 
which,  at  the  time  of  the  inspection,  were  grossly  infested  with  ticks. 
Three  sheep,  or  about  2  per  cent  of  the  entire  flock,  were  found  in- 
fested with  live  ticks.  Dead  ticks  alone  were  found  on  31  sheep,  or 
25  per  cent  of  the  flock.  Rams  were  the  hosts  for  the  live  ticks  in  all 
three  cases,  and  in  the  case  of  two  of  them  the  ticks  were  attached  to 
the  scrotum.  One  ram  had  two  ticks,  a  female  just  after  the  second 
molt  and  another  one-third  engorged;  another  had  but  one  tick,  a 


36  BIOLOGY   OF    THE    TEXAS-FEVER   TICK. 

female,  newly  molted,  and  the  remaining  one  had  a  half-grown  female 
on  the  hairy  portion  of  the  leg.  The  wool  of  the  first  was  moderately 
oily  and  that  of  the  other  two  not  oily. 

Dead  ticks  were  found  on  32  sheep.  This  includes  one  that  also 
had  live  ticks.  Ticks  in  the  larval  stage  were  found  on  all  these  sheep, 
and  in  addition  one  dead  male  was  present  in  each  of  four  instances. 
The  larvae  were  attached  to  the  skin  of  the  woolly  regions  of  the  body. 
When  they  were  removed  a  small  scale  of  epidermis  of  the  host  was 
brought  way  with  the  mouth  parts,  indicating  that  the  larvae  had 
actually  taken  hold.  The  males  were  found  unattached  in  the  wool. 
The  condition  of  the  wool  of  the  entire  flock  was  noted  for  the  purpose 
of  determining,  if  possible,  whether  the  amount  of  oil  on  the  wool  plays 
any  part  in  preventing  ticks  attaching  to  sheep.  Eighty-six  sheep,  or 
69  per  cent,  had  wool  not  oily;  38  sheep,  or  30  per  cent,  had  wool 
moderately  oily;  and  1  sheep,  or  about  1  per  cent,  had  oily  wool. 
Twenty-seven  per  cent  of  the  first  class,  29  per  cent  of  the  second 
class,  and  zero  per  cent  of  the  third  class  of  sheep  carried  ticks  either 
dead  or  alive.  From  this  it  would  appear  that  the  relative  amount 
of  oil  on  the  wool  bears  no  important  relation  to  the  presence  of  ticks. 

Summarizing  the  results  of  the  observations  on  the  natural  infesta- 
tion of  sheep,  it  may  be  said  that  live  ticks  were  found  on  the  ears, 
neck,  legs,  abdomen,  and  scrotum.  In  no  case  were  they  present  in 
great  numbers.  Rams  seem  to  be  much  more  favorable  hosts  than 
ewes.  Taking  into  account  all  the  inspections  made,  ticks  were  found 
on  rams  eight  times  and  on  ewes  twice.  In  view  of  the  large  number 
of  ewes  inspected  as  compared  with  the  rams  this  result  can  not  be 
considered  accidental. 

THE     PROGENY     OF     FEMALES     MATURED     ON     SHEEP     NONINFECTIOUS. 

As  previously  stated,  two  of  the  female  ticks  that  matured  on  sheep 
laid  viable  eggs.  One  collected  October  16,  1907,  began  to  lay 
October  23,  1907;  hatching  began  April  9.  and  ended  April  17,  1908. 
The  other,  collected  October  14,  1907,  began  to  lay  October  22  and 
hatching  began  April  11,  1908. 

On  May  2,  1908,  the  larvae  from  the  above  ticks  were  placed  on  a 
northern  cow  (No.  603)  about  10  years  old,  at  the  Bureau  of  Animal 
Industry  Experiment  Station,  Bethesda,  Md.  Six  hundred  and 
forty-three  females  matured,  but  the  cow  continued  well  and  in 
good  condition,  the  temperature  and  number  of  erythrocytes  remain- 
ing normal. 

On  July  15,  1908,  the  progeny  of  ticks  collected  from  the  above 
cow,  May  28,  1908,  were  placed  on  two  northern  cattle,  a  bull  (No. 
585)  and  a  heifer  (No.  591),  each  about  1  year  old.  The  temperature 
of  both  animals  remained  normal. 


MAN   AS   A   HOST   OF   THE   TICK.  37 

On  September  14,  1908,  and  a  number  of  times  thereafter  three 
northern  heifers  (Xos.  582,  583,  584),  each  about  1J  years  old,  were 
infested  with  the  progeny  of  ticks  collected  from  bull  No.  585,  August 
8,  1908,  but  none  of  them  developed  fever. 

The  above  experiments  show  that  the  larvae  were  noninfectious, 
but  it  is  not  known,  of  course,  whether  the  two  females  of  which 
they  were  the  progeny  belonged  to  an  infectious  brood,  and  further- 
more, if  this  were  the  case,  it  could  not  be  known  whether  the  two 
females  were  infectious  or  not  in  their  larval  state,  since  it  is  fair  to 
assume  that  only  a  certain  per  cent  of  the  progeny  of  infectious  ticks 
are  infectious.  Since,  however,  the  particular  sheep  from  which  they 
were  collected  ran  on  a  pasture  where  infectious  ticks  undoubtedly 
occurred  and  since  ticks  had  been  observed  on  this  sheep  a  number  of 
times,  the  chances  are,  if  the  Texas-fever  parasite  could  survive  in  the 
blood  of  sheep,  the  blood  of  this  one  would  have  been  infectious  and 
at  least  some  of  the  progeny  of  the  two  females  would  have  proved 
infectious. 

MAN    AS    A    HOST    OF   THE    TICK. 

So  far  as  known  the  cattle  tick  in  its  larval  stage  does  not  attack 
man.  Persons  handling  these  larvae  in  the  laboratory  and  passing 
through  fields  infested  with  only  cattle  ticks  are  not  attacked.  Ran- 
som 17  (1906)  reports  two  experimental  and  one  accidental  attachment 
of  adults  that  molted  in  the  laboratory.  Below  are  records  of  the 
attachment  of  ticks  to  man,  obtained  in  the  course  of  the  present 
investigations. 

On  June  18,  1907,  11.30  a.  m.,  a  female  specimen  of  Margaropus 
annulatus  about  one-third  engorged  was  placed  on  the  calf  of  the  leg. 
Shortly  after  noon  it  attached  itself.  It  was  removed  June  19,  2.45 
p.  m.,  having  drawn  blood  for  more  than  24  hours.  At  this  time  it- 
had  attained  two-thirds  of  the  usual  size  of  an  engorged  tick.  The 
place  where  it  was  attached  became  highly  inflamed,  acquiring  a 
purplish  color. 

On  August  13,  1907,  a  female  that  had  molted  in  the  laboratory 
on  August  7  was  placed  on  the  thigh.  The  tick  attached  itself,  but 
thereafter  changed  its  location  many  times.  It  was  present  for 
several  days  and  then. disappeared. 

On  August  27  a  nymph,  shortly  after  the  iirst  molt,  was  placed  on  the 
arm.  It  attached  itself  and  remained  so  for  several  hours  and  then 
disappeared,  probably  having  been  dislodged  by  the  clothing. 


38  BIOLOGY   OF   THE   TEXAS-FEVER  TICK. 


BIBLIOGRAPHY. 

The  following  list  contains  only  works  referred  to  in  this  bulletin: 

1.  COTTON,   E.  C.     Tick  eradication.     The  life  history  and  habits  of  the  North 

American  fever  tick  with  special  reference  to  eradication.  Tennessee  Agricul- 
tural Experiment  Station  of  University  of  Tennessee,  Bulletin  81.  Knox- 
ville,  1908. 

2.  CURTICE,   COOPER.     The  biology  of  the  cattle  tick.     Journal  of  Comparative 

Medicine  and  Verterinary  Archives,  vol.  12,  No.  7,  pp.  313-319.  New  York, 
July,  1891. 

3.  About   cattle   ticks.     Journal   of    Comparative   Medicine   and   Veterinary 
Archives,  vol.  13,  No.  1,  pp.  1-7.     New  York,  January,  1892. 

4.  The  cattle  tick  (Boophilus  boi'is  Rileysp.).     Texas  Agricultural  Experiment 
Station,  Bulletin  24.     Bryan,  1892. 

5.  On  the  extermination  of  the  cattle  tick  and  the  disease  spread  by  it.     Journal 
of  Comparative  Medicine  and  Veterinary  Archives,  vol.  17,  No.  9,  pp.  649-655. 
Philadelphia,  September,  1896. 

6.  The  cattle-tick  plague,  and  what  may  be  done  to  prevent  it.     Southern 
Planter,  vol.  58,  No.  1,  pp.  24-27.     Richmond,  January,  1897. 

7.  DALRYMPLE,  W.  H.,  MORGAN,  H.  A.,  and  DODSON,  W.  R.     Cattle  tick  and  Texas 

fever.  Louisiana  Agricultural  Experiment  Station,  Bulletin  51,  Second  series. 
Baton  Rouge,  1898. 

8.  DINWIDDIE,  R.  R.     Animal  parasitism.     Some  Texas  fever  experiments,  Arkan- 

sas Agricultural  Experiment  Station,  Bulletin  20.     Little  Rock,  1892. 

9.  Notes  on  the  cattle  tick  and  the  tick  fever  of  cattle.     Arkansas  Agricultural 
Experiment  Station,  Bulletin  101.     Fayetteville,  1908. 

10.  GRAYBILL,  H.  \V.     Methods  of  exterminating  the  Texas-fever  tick.     United  States 

Department  of  Agriculture,  Farmers'  Bulletin  378.     Washington,  1909. 

11.  HUNTER,  W.  D.     Note  on  the  occurrence  of  the  North  American  fever  tick  on 

sheep.  United  States  Department  of  Agriculture,  Bureau  of  Entomology, 
Circular  91.  Washington,  1907. 

12.  HUNTER,  W.  D.,  and  HOOKER,  W.  A.     Information  concerning  the  North  Ameri- 

can fever  tick,  with  notes  on  other  species.  United  States  Department  of 
Agriculture,  Bureau  of  Entomology,  Bulletin  72.  Washington,  1907. 

13.  MORGAN,  H.  A.     Ticks  and  Texas  fever.     Louisiana  Agricultural  Experiment 

Station,  Bulletin  56,  second  series.     Baton  Rouge,  1899. 

14.  The  cattle-tick  situation.     Proceedings  of    the    Society  for    Promotion  of 
Agricultural  Science,   Twenty-fourth  Annual  Meeting,  pp.  72-74.     Washing- 
ton, 1903. 

15.  The  Texas  fever  cattle-tick  situation  and  the  eradication  of  the  tick  by  a 
pasture  rotation  system.     Louisiana  Agricultural  Experiment  Station,  Bulletin 
82,  second  series.     Baton  Rouge,  1905. 

16.  NEWELL,  WILMON,  and  DOUGHERTY,  M.  S.     The  cattle  tick  (Boophilus  annulatus). 

Studies  of  the  egg  and  seed-tick  stages.  A  simple  method  of  eradicating  the 
tick.  Louisiana  State  Crop  Pest  Commission,  Circular  10.  Baton  Rouge,  1906. 

17.  RANSOM,  B.  H.     Some  unusual  host  relations  of  the  Texas-fever  tick.     United 

States  Department  of  Agriculture,  Bureau  of  Animal  Industry,  Circular  98. 
Washington,  1906. 

18.  SCHROEDER,  E.  C.     A  note  on  the  vitality  of  the  southern  cattle  tick.     United 

States  Department  of  Agriculture,  Bureau  of  Animal  Industry,  Sixteenth 
Annual  Report,  1899,  pp.  41-42.  Washington,  1900. 


BIBLIOGRAPHY.  39 

19.  SCHKOEDER,  E.  C.     Notes  on  the  cattle  tick  and  Texas  fever.     United  States 

Department  of  Agriculture,  Bureau  of  Animal  Industry,  Twenty-second 
Annual  Report,  1905,  pp.  49-70.  Washington,  1907. 

20.  SCHROEDER,  E.  C.,  and  COTTON,  W.  E.     The  growing  of  noninfected  ticks  and 

afterwards  infecting  them.  United  States  Department  of  Agriculture,  Bureau 
of  Animal  Industry,  Sixteenth  Annual  Report,  1899,  pp.  33-41.  Washington, 
1900. 

21.  The  persistence  of  the  Texas-fever  organism  in  the  blood  of  southern  cattle. 
United  States  Department  of  Agriculture,  Bureau  of  Animal  Industry,  Twenty 
second  Annual  Report,  1905,  pp.  71-78.     Washington,  1907. 

22.  SMITH,  THEOBALD,  and  KJLBORNE,  F.  L.     Investigations  into  the  nature,  causa- 

tion, and  prevention  of  Texas  or  southern  cattle  fever.  United  States  Depart- 
ment of  Agriculture,  Bureau  of  Animal  industry,  Bulletin  1.  Washington,  1893. 


APPENDIX. 


TABLE  1. — Individual  records  of  ticks  used  in  experiments. 


Num- 
ber of 
tick. 

Date  col- 
lected. 

Number 
of  eggs  de- 
posited. 

Preovi- 
position 
period. 

Ovi- 
position 
period. 

Incuba- 
tion pe- 
riod. 

Hatch- 
ing pe- 
riod. 

Mini- 
mum 
longev- 
ity. 

Maxi- 
mum 
longev- 
ity. 

Entire 
time. 

Per  cent 
hatched. 

I... 

2 

1907 
June    1 
do. 

630 

2,276 

Days. 

Days. 
4 
10 

Days. 
24  to  32 
24  to  31 

Days^ 
11 

Days. 
13 
9 

Days. 
50 
46 

Days. 
83 
79 

86 
94 

3. 

do.      . 

877 

7 

5 

24  to  32 

5 

52 

85 

x    93 

4  

..do.... 

3,095 

6 

13 

23  to  31 

12 

4 

48 

83 

91 

5 

do 

1,036 

7 

3 

25  to  34 

11 

15 

54 

88 

93 

6  a... 

do    . 

2,150 

9 

9 

23  to  31 

10 

7 

65 

100 

73 

7  a... 

.    do  

2,614 

6 

14 

22  to  33 

10 

3 

55 

90 

95 

8  
9. 

July     1 
.do...  . 

3,000 
3,562 

4 

4 

17 
18 

20  to  25 
20  to  25 

11 

17 

22 
16 

'      82 
62 

112 
91 

% 
96 

10... 

...do.... 

1,863 

4 

5 

20  to  27 

9 

20 

85 

112 

97 

11. 

do 

3,515 

4 

20 

19  to  25 

15 

16 

103 

95 

12  
13a.... 

...do.    .. 
...do.... 

1,858 
3,820 

4 

4 

4 
16 

20  to  25 
19  to  25 

4 
15 

24 
20 

55 

67 

82 
98 

90 

94 

14<J 

do 

2,814 

3 

10 

20  to  25 

9 

19 

79 

109 

% 

15  

16  

Aug.    1 
.  .do  

3,683 
2,972 

3 
3 

15 
18' 

20  to  25 
20  to  24 

8 
15 

22 
10 

160 

187 

187 
218 

90 
96 

17 

do 

2,536 

3 

15 

20  to  25 

15 

4 

15'-> 

180 

97 

18  
19  

...do  
...do 

2,820 
2,700 

3 
3 

17 
12 

19  to  25 
20  to  27 

16 
14 

9 
11 

170 
192 

198 
221 

98 
97 

20a  ... 
21o.... 
22  
23.   . 

...do.... 
...do  
Aug.  31 
do    . 

1,851 
2,267 
2,809 
2,699 

3 
3 
3 
3 

13 
19 
19 

18 

20  to  25 
21  to  26 
28  to  54 
29  to  48 

12 
14 
39 
31 

6 
9 
5 
13 

144 
192 
224 
204 

172 
221 
258 
240 

98 
94 
83 
95 

24.   ... 

...do.... 

2,049 

4 

15 

30  to  50 

31 

7 

1% 

234 

66 

25 

do. 

2,266 

3 

19 

30  to  66 

49 

11 

219 

270 

57 

26. 

.do  .. 

2,262 

4 

14 

29  to  52 

34 

i 

234 

272 

95 

27  a 

do 

39 

4 

9 

(6) 

28  a 

do 

2,344 

2 

14 

29  to  50 

32 

7 

192 

230 

97 

34  
35...   . 

Oct.     1 
...do.... 

2,780 
2,942 

4 
4 

36 
34 

167  to  182 
170  to  185 

21 
26 

5 

8 

91 

85 

276 
276 

90 

87 

36 

do 

2,838 

4 

36 

166  to  186 

31 

5 

94 

276 

92 

37. 

.do.      . 

2,570 

4 

37 

169  to  186 

25 

4 

92 

281 

77 

38  

...do.... 

3,383 

4 

35 

170  to  186 

24 

4 

99 

288 

82 

39" 

do 

960 

6 

21 

173  to  188 

16 

3 

98 

281 

80 

40«  ... 
45  
46 

.  ..do..  .  . 
Nov.    1 
do  . 

2,467 
2,961 
1,936 

4 

7 
9 

31 
99 

81 

165  to  185 
151  to  170 
139  to  158 

29 

13 
11 

3 

8 
9 

90 
69 
60 

279 
239 
236 

84 
6 
4 

47.   . 

...do... 

2,281 

10 

80 

118  to  125 

7 

21 

37 

213 

.09 

48 

do 

991 

20 

118 

154 

0 

25 

25 

200 

.1 

49 

do  . 

2,855 

8 

151 

138  to  158 

13 

13 

76 

244 

4 

50a  

...do.... 

1,985 

9 

82 

117tol68 

15 

21 

78 

253 

3 

51  a      . 

do 

1,896 

9 

78 

122  to  169 

18 

5 

73 

244 

/ 

61 

Nov    30 

(c) 

62 

do 

3,207 

58 

54 

57 

4 

20 

27 

187 

1 

63 

do 

2,103 

98 

20 

50  to  60 

11 

10 

91 

249 

18 

64.     .. 

..do... 

3,023 

38 

87 

51  to  68 

11 

7 

57 

215 

4 

65 

do 

357 

70 

40 

(b) 

• 

72 

Dec    29 

(c) 

73 

..  do 

3,180 

63 

18 

56  to  66 

14 

13 

46 

181 

1 

74 

.do. 

4,272 

39 

63 

48  to  80 

25 

7 

73 

207 

35 

75 

do 

1  970 

46 

37 

(6) 

76  

77 

1908 
Jan.      1 

1907 
Dec    30 

3,  173 

(c) 

63 

24 

48  to  07 

14 

8 

69 

201 

25 

82... 
83  

1908 
Feb.     4 
Feb.     3 

4,276 
3,900 

28 
29 

39 
36 

48  to  65 
45  to  62 

26 
25 

4 

6 

99 
76 

189 
172 

81 

86 

a  Eggs  were  not  counted, 
larvae  had  died. 
6  Eggs  failed  to  hatch, 
c  Did  not  oviposit. 

40 


The  unhatched  eggs  and  the  larvae  in  each  tube  were  counted  after  all  the 


APPENDIX.  41 

TABLE  1. — Individual  records  of  ticks  used  in  experiments — Continued. 


Num- 
ber of 
tick. 

Date  col- 
lected. 

Number 
of  eggs  de- 
posited. 

Preovi- 
posilion 
period. 

Ovi- 
posit ion 
period. 

Incuba- 
tion pe- 
riod. 

Hatch- 
ing pe- 
riod. 

Mini- 
mum 
longev- 
ity. 

Maxi- 
mum 
longev- 
ity. 

Entire 
time. 

Per  cent 
hatched. 

84... 
85  

87 

1908 
Feb.     4 
Jan.    30 
.do  

806 
3,620 
3,725 

Days. 
36 
35 
34 

Days. 
22 
33 
43 

Days. 
53  to  63 
49  to  63 
48  to  64 

Days. 
14 
26 
26 

Days. 

6 
7 
2 

Days. 

77 
86 
81 

Days. 

177 
186 
176 

39 
t>5 
72 

88<J..  . 

89a. 

Jan.    29 
do 

3,269 
3,718 

37 
37 

36 
41 

48  to  65 
47  to  65 

25 

18 

7 
21 

59 
64 

156 
156 

34 
14 

95  
98o.... 
105.... 
106 

Feb.  27 
Feb.  28 
Mar.  26 
do  

2,302 
2,925 
4,559 
2,680 

10 

8 
5 
6 

24 
36 
34 
24 

47  to  64 
45  to  62 
36  to  53 
43  to  53 

18 
27 
13 
12 

4 
2 
7 

7 

94 
80 
90 
98 

162 
143 
149 
155 

62 
96 
77 

78 

107 

.  .do  

2,731 

8 

14 

43  to  52 

15 

12 

101 

161 

66 

108 

do 

3,024 

5 

17 

44  to  53 

12 

11 

101 

159 

89 

109 

do 

4,035 

6 

23 

39  to  53 

14 

6 

97 

155 

95 

liofc.. 

lllfr.  . 
1126 

Mar.  29 
...do  
do 

3,712 
3,405 
3.622 

4 
5 
4 

35 
27 
26 

37  to  52 
38  to  51 
39  to  51 

14 
16 
14 

13 
5 
5 

92 
89 

88 

146 
144 

144 

92 
92 

97 

113  fr 

do  . 

3,796 

4 

25 

37  to  51. 

15 

10 

103 

156 

93 

125.... 
126 

Apr.  29 
...do  

4,244 
3,966 

4 
6 

22 
19 

24  to  36 
26  to  34 

18 
12 

5 
6 

113 

89 

152 

128 

96 
33 

127 

do 

3,929 

6 

25 

24  to  33 

18 

4 

118 

156 

98 

128 

do  . 

4.385 

4 

24 

25  to  36 

16 

9 

116 

156 

96 

129 

.do  

5,105 

6 

24 

24  to  33 

18 

7 

116 

154 

84 

130  &.  . 

...do  

3,942 

6 

23 

24  to  33 

17 

9 

105 

145 

98 

1316.. 

...do... 

3,949 

7 

19 

23  to  33 

13 

10 

93 

133 

98 

132  b  .  . 
1336. 

...do  
.do 

4,035 
3,246 

6 

7 

27 
21 

24  to  33 
24  to  32 

17 
18 

6 
10 

128 
79 

173 

122 

98 
93 

134  o  .. 

..do  

6 

24 

23  to  33 

22 

5 

92 

131 

135  a.  . 

...do... 

5 

22 

25  to  34 

19 

11 

% 

138 

136  a 

do 

G 

21 

24  to  33 

16 

6 

91 

131 

137  a 

do. 

6 

26 

25  to  34 

17 

19 

94 

131 

138  c.  . 

...do  

22 

24  to  32 

20 

108 

149 

a  Eggs  were  placed  in  test  tubes  directly  on  moist  sand.  No  water  was  added  to  the  sand  after  the  tube 
was  made. 

ft  Eggs  were  placed  in  test  tubes  provided  with  two  cardboard  disks.  No  water  was  added  to  the 
sand  after  the  tube  was  made. 

c  Eggs  were  floated  on  water  in  test  tubes. 


42 


BIOLOGY   OF    THE    TEXAS-FEVER   TICK. 


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